Fix TLS alert codes

Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index a4cf44c..976a87c 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -3610,7 +3610,7 @@
     {
         MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad finished message" ) );
         mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,
-                                        MBEDTLS_SSL_ALERT_MSG_DECODE_ERROR );
+                                        MBEDTLS_SSL_ALERT_MSG_DECRYPT_ERROR );
         return( MBEDTLS_ERR_SSL_BAD_HS_FINISHED );
     }