replace md_max_size with tls13_md_max_size

Signed-off-by: Jerry Yu <jerry.h.yu@arm.com>
diff --git a/library/ssl_misc.h b/library/ssl_misc.h
index ceaf058..904d8c7 100644
--- a/library/ssl_misc.h
+++ b/library/ssl_misc.h
@@ -521,10 +521,10 @@
 
 typedef struct
 {
-    unsigned char client_application_traffic_secret_N[ MBEDTLS_MD_MAX_SIZE ];
-    unsigned char server_application_traffic_secret_N[ MBEDTLS_MD_MAX_SIZE ];
-    unsigned char exporter_master_secret             [ MBEDTLS_MD_MAX_SIZE ];
-    unsigned char resumption_master_secret           [ MBEDTLS_MD_MAX_SIZE ];
+    unsigned char client_application_traffic_secret_N[ MBEDTLS_TLS1_3_MD_MAX_SIZE ];
+    unsigned char server_application_traffic_secret_N[ MBEDTLS_TLS1_3_MD_MAX_SIZE ];
+    unsigned char exporter_master_secret             [ MBEDTLS_TLS1_3_MD_MAX_SIZE ];
+    unsigned char resumption_master_secret           [ MBEDTLS_TLS1_3_MD_MAX_SIZE ];
 } mbedtls_ssl_tls1_3_application_secrets;
 
 /*