Refactor key_schedule_stage_handshake

Signed-off-by: Jerry Yu <jerry.h.yu@arm.com>
diff --git a/library/ssl_tls13_client.c b/library/ssl_tls13_client.c
index 57a0b28..8a167a5 100644
--- a/library/ssl_tls13_client.c
+++ b/library/ssl_tls13_client.c
@@ -1297,7 +1297,7 @@
     }
 
     /* Compute handshake secret */
-    ret = mbedtls_ssl_tls1_3_key_schedule_stage_handshake( ssl );
+    ret = mbedtls_ssl_tls13_key_schedule_stage_handshake( ssl );
     if( ret != 0 )
     {
         MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_tls1_3_derive_master_secret", ret );