ssl_cache: Error renaming and document improvement

Signed-off-by: Pengyu Lv <pengyu.lv@arm.com>

include/mbedtls/ssl.h

@@ -111,7 +111,7 @@
 /* Error space gap */
 /* Error space gap */
 /** Cache entry not found */
-#define MBEDTLS_ERR_SSL_CACHE_NOT_FOUND                   -0x7E80
+#define MBEDTLS_ERR_SSL_CACHE_ENTRY_NOT_FOUND             -0x7E80
 /** Memory allocation failed */
 #define MBEDTLS_ERR_SSL_ALLOC_FAILED                      -0x7F00
 /** Hardware acceleration function returned with error */

include/mbedtls/ssl_cache.h

@@ -104,7 +104,8 @@ void mbedtls_ssl_cache_init(mbedtls_ssl_cache_context *cache);
  *                        associated with \p session_id, if present.
  *
  * \return                \c 0 on success.
- * \return                A negative error code on failure.
+ * \return                #MBEDTLS_ERR_SSL_CACHE_ENTRY_NOT_FOUND if there is
+ *                        no cache entry with specified session ID found.
  */
 int mbedtls_ssl_cache_get(void *data,
                           unsigned char const *session_id,

library/ssl_cache.c

@@ -51,7 +51,7 @@ static int ssl_cache_find_entry(mbedtls_ssl_cache_context *cache,
                                 size_t session_id_len,
                                 mbedtls_ssl_cache_entry **dst)
 {
-    int ret = MBEDTLS_ERR_SSL_CACHE_NOT_FOUND;
+    int ret = MBEDTLS_ERR_SSL_CACHE_ENTRY_NOT_FOUND;
 #if defined(MBEDTLS_HAVE_TIME)
     mbedtls_time_t t = mbedtls_time(NULL);
 #endif