ssl_cache: Error renaming and document improvement

Signed-off-by: Pengyu Lv <pengyu.lv@arm.com>
diff --git a/include/mbedtls/ssl.h b/include/mbedtls/ssl.h
index 1e51745..0588e0c 100644
--- a/include/mbedtls/ssl.h
+++ b/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 */