doxygen: fix parameter name typos and misused \p commands

\p is reserved for function parameters.
\c is used to describe other values and variables.
Signed-off-by: Andrzej Kurek <andrzej.kurek@arm.com>
diff --git a/include/mbedtls/cipher.h b/include/mbedtls/cipher.h
index 03e2327..bdfa7f8 100644
--- a/include/mbedtls/cipher.h
+++ b/include/mbedtls/cipher.h
@@ -505,7 +505,7 @@
  *
  * \return              The cipher name, which is a human readable string,
  *                      with static storage duration.
- * \return              \c NULL if \c info is \p NULL.
+ * \return              \c NULL if \p info is \c NULL.
  */
 static inline const char *mbedtls_cipher_info_get_name(
     const mbedtls_cipher_info_t *info)
@@ -596,7 +596,7 @@
 }
 
 /**
- * \brief               This function initializes a \p cipher_context as NONE.
+ * \brief               This function initializes a \p ctx as NONE.
  *
  * \param ctx           The context to be initialized. This must not be \c NULL.
  */
@@ -790,7 +790,7 @@
  * \param ctx           The context of the cipher. This must be initialized.
  *
  * \return              The key length of the cipher in bits.
- * \return              #MBEDTLS_KEY_LENGTH_NONE if ctx \p has not been
+ * \return              #MBEDTLS_KEY_LENGTH_NONE if \p ctx has not been
  *                      initialized.
  */
 static inline int mbedtls_cipher_get_key_bitlen(
@@ -990,7 +990,7 @@
  * \param ctx           The generic cipher context. This must be initialized and
  *                      bound to a key.
  * \param output        The buffer to write data to. This needs to be a writable
- *                      buffer of at least \p block_size Bytes.
+ *                      buffer of at least \c block_size Bytes.
  * \param olen          The length of the data written to the \p output buffer.
  *                      This may not be \c NULL.
  *