Make \retval commands non-empty

Pacify Clang >=15 which complained:
```
include/psa/crypto.h:91:23: error: empty paragraph passed to '\retval' command [-Werror,-Wdocumentation]
 * \retval #PSA_SUCCESS
   ~~~~~~~~~~~~~~~~~~~^
```

This commit performs the following systematic replacement:
```
perl -i -0777 -p -e 's/([\\@])(retval +\S+)\n(?! *\*? *([^\n \\*\/]|\\[cp]\b))/$1$2 ${1}emptydescription\n/g' $(git ls-files '*.[hc]' '*.function' '*.jinja')
```
i.e. add an `\emptydescription` argument to `\retval` commands (or
`@retval`, which we don't normally used) that are followed by a single word,
unless the next line looks like it contains text which would be the
description.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/library/psa_crypto_storage.h b/library/psa_crypto_storage.h
index 8e108c5..04768f8 100644
--- a/library/psa_crypto_storage.h
+++ b/library/psa_crypto_storage.h
@@ -96,14 +96,14 @@
  * \param[in] data          Buffer containing the key data.
  * \param data_length       The number of bytes that make up the key data.
  *
- * \retval #PSA_SUCCESS
- * \retval #PSA_ERROR_INVALID_ARGUMENT
- * \retval #PSA_ERROR_INSUFFICIENT_MEMORY
- * \retval #PSA_ERROR_INSUFFICIENT_STORAGE
- * \retval #PSA_ERROR_STORAGE_FAILURE
- * \retval #PSA_ERROR_ALREADY_EXISTS
- * \retval #PSA_ERROR_DATA_INVALID
- * \retval #PSA_ERROR_DATA_CORRUPT
+ * \retval #PSA_SUCCESS \emptydescription
+ * \retval #PSA_ERROR_INVALID_ARGUMENT \emptydescription
+ * \retval #PSA_ERROR_INSUFFICIENT_MEMORY \emptydescription
+ * \retval #PSA_ERROR_INSUFFICIENT_STORAGE \emptydescription
+ * \retval #PSA_ERROR_STORAGE_FAILURE \emptydescription
+ * \retval #PSA_ERROR_ALREADY_EXISTS \emptydescription
+ * \retval #PSA_ERROR_DATA_INVALID \emptydescription
+ * \retval #PSA_ERROR_DATA_CORRUPT \emptydescription
  */
 psa_status_t psa_save_persistent_key(const psa_core_key_attributes_t *attr,
                                      const uint8_t *data,
@@ -129,11 +129,11 @@
  * \param[out] data         Pointer to an allocated key data buffer on return.
  * \param[out] data_length  The number of bytes that make up the key data.
  *
- * \retval #PSA_SUCCESS
- * \retval #PSA_ERROR_INSUFFICIENT_MEMORY
- * \retval #PSA_ERROR_DATA_INVALID
- * \retval #PSA_ERROR_DATA_CORRUPT
- * \retval #PSA_ERROR_DOES_NOT_EXIST
+ * \retval #PSA_SUCCESS \emptydescription
+ * \retval #PSA_ERROR_INSUFFICIENT_MEMORY \emptydescription
+ * \retval #PSA_ERROR_DATA_INVALID \emptydescription
+ * \retval #PSA_ERROR_DATA_CORRUPT \emptydescription
+ * \retval #PSA_ERROR_DOES_NOT_EXIST \emptydescription
  */
 psa_status_t psa_load_persistent_key(psa_core_key_attributes_t *attr,
                                      uint8_t **data,
@@ -148,7 +148,7 @@
  * \retval #PSA_SUCCESS
  *         The key was successfully removed,
  *         or the key did not exist.
- * \retval #PSA_ERROR_DATA_INVALID
+ * \retval #PSA_ERROR_DATA_INVALID \emptydescription
  */
 psa_status_t psa_destroy_persistent_key(const mbedtls_svc_key_id_t key);
 
@@ -190,9 +190,9 @@
  * \param[out] attr            On success, the attribute structure is filled
  *                             with the loaded key metadata.
  *
- * \retval #PSA_SUCCESS
- * \retval #PSA_ERROR_INSUFFICIENT_MEMORY
- * \retval #PSA_ERROR_DATA_INVALID
+ * \retval #PSA_SUCCESS \emptydescription
+ * \retval #PSA_ERROR_INSUFFICIENT_MEMORY \emptydescription
+ * \retval #PSA_ERROR_DATA_INVALID \emptydescription
  */
 psa_status_t psa_parse_key_data_from_storage(const uint8_t *storage_data,
                                              size_t storage_data_length,
@@ -322,10 +322,10 @@
  * You may call this function multiple times during a transaction to
  * atomically update the transaction state.
  *
- * \retval #PSA_SUCCESS
- * \retval #PSA_ERROR_DATA_CORRUPT
- * \retval #PSA_ERROR_INSUFFICIENT_STORAGE
- * \retval #PSA_ERROR_STORAGE_FAILURE
+ * \retval #PSA_SUCCESS \emptydescription
+ * \retval #PSA_ERROR_DATA_CORRUPT \emptydescription
+ * \retval #PSA_ERROR_INSUFFICIENT_STORAGE \emptydescription
+ * \retval #PSA_ERROR_STORAGE_FAILURE \emptydescription
  */
 psa_status_t psa_crypto_save_transaction(void);
 
@@ -339,9 +339,9 @@
  *         #psa_crypto_transaction.
  * \retval #PSA_ERROR_DOES_NOT_EXIST
  *         There is no ongoing transaction.
- * \retval #PSA_ERROR_STORAGE_FAILURE
- * \retval #PSA_ERROR_DATA_INVALID
- * \retval #PSA_ERROR_DATA_CORRUPT
+ * \retval #PSA_ERROR_STORAGE_FAILURE \emptydescription
+ * \retval #PSA_ERROR_DATA_INVALID \emptydescription
+ * \retval #PSA_ERROR_DATA_CORRUPT \emptydescription
  */
 psa_status_t psa_crypto_load_transaction(void);
 
@@ -380,8 +380,8 @@
  *
  * \retval #PSA_SUCCESS
  *         Success
- * \retval #PSA_ERROR_STORAGE_FAILURE
- * \retval #PSA_ERROR_INSUFFICIENT_STORAGE
+ * \retval #PSA_ERROR_STORAGE_FAILURE \emptydescription
+ * \retval #PSA_ERROR_INSUFFICIENT_STORAGE \emptydescription
  * \retval #PSA_ERROR_NOT_PERMITTED
  *         The entropy seed file already exists.
  */