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/include/psa/crypto_extra.h b/include/psa/crypto_extra.h
index b62acdb..fa3e383 100644
--- a/include/psa/crypto_extra.h
+++ b/include/psa/crypto_extra.h
@@ -187,12 +187,12 @@
  *         or the specified slot number is not valid.
  * \retval #PSA_ERROR_NOT_PERMITTED
  *         The caller is not authorized to register the specified key slot.
- * \retval #PSA_ERROR_INSUFFICIENT_MEMORY
- * \retval #PSA_ERROR_INSUFFICIENT_STORAGE
- * \retval #PSA_ERROR_COMMUNICATION_FAILURE
- * \retval #PSA_ERROR_DATA_INVALID
- * \retval #PSA_ERROR_DATA_CORRUPT
- * \retval #PSA_ERROR_CORRUPTION_DETECTED
+ * \retval #PSA_ERROR_INSUFFICIENT_MEMORY \emptydescription
+ * \retval #PSA_ERROR_INSUFFICIENT_STORAGE \emptydescription
+ * \retval #PSA_ERROR_COMMUNICATION_FAILURE \emptydescription
+ * \retval #PSA_ERROR_DATA_INVALID \emptydescription
+ * \retval #PSA_ERROR_DATA_CORRUPT \emptydescription
+ * \retval #PSA_ERROR_CORRUPTION_DETECTED \emptydescription
  * \retval #PSA_ERROR_BAD_STATE
  *         The library has not been previously initialized by psa_crypto_init().
  *         It is implementation-dependent whether a failure to initialize
@@ -487,10 +487,10 @@
  *                              according to \p type as described above.
  * \param data_length           Size of the \p data buffer in bytes.
  *
- * \retval #PSA_SUCCESS
- * \retval #PSA_ERROR_INVALID_ARGUMENT
- * \retval #PSA_ERROR_NOT_SUPPORTED
- * \retval #PSA_ERROR_INSUFFICIENT_MEMORY
+ * \retval #PSA_SUCCESS \emptydescription
+ * \retval #PSA_ERROR_INVALID_ARGUMENT \emptydescription
+ * \retval #PSA_ERROR_NOT_SUPPORTED \emptydescription
+ * \retval #PSA_ERROR_INSUFFICIENT_MEMORY \emptydescription
  */
 psa_status_t psa_set_key_domain_parameters(psa_key_attributes_t *attributes,
                                            psa_key_type_t type,
@@ -517,8 +517,8 @@
  * \param[out] data_length      On success, the number of bytes
  *                              that make up the key domain parameters data.
  *
- * \retval #PSA_SUCCESS
- * \retval #PSA_ERROR_BUFFER_TOO_SMALL
+ * \retval #PSA_SUCCESS \emptydescription
+ * \retval #PSA_ERROR_BUFFER_TOO_SMALL \emptydescription
  */
 psa_status_t psa_get_key_domain_parameters(
     const psa_key_attributes_t *attributes,