env: Setup GD_FLG_ENV_DEFAULT flag when default environment are used

Setup flag when default environment are used to be able to
rewrite default distro boot variables based on SoC boot mode.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Alexander Graf <agraf@suse.de>

common/env_common.c

@@ -123,6 +123,7 @@ void set_default_env(const char *s)
 		error("Environment import failed: errno = %d\n", errno);
 
 	gd->flags |= GD_FLG_ENV_READY;
+	gd->flags |= GD_FLG_ENV_DEFAULT;
 }