env: mmc: Fix test for ENV_IS_EMBEDDED

The symbol "ENV_IS_EMBEDDED" is an environment internal define and not a
real CONFIG symbol. The IS_ENABLED() macro is still valid to use here,
so update the check.

Signed-off-by: Tom Rini <trini@konsulko.com>

env/mmc.c

@@ -553,7 +553,7 @@ err:
 
 static int env_mmc_load(void)
 {
-	if (IS_ENABLED(CONFIG_ENV_IS_EMBEDDED))
+	if (IS_ENABLED(ENV_IS_EMBEDDED))
 		return 0;
 	else if (IS_ENABLED(CONFIG_SYS_REDUNDAND_ENVIRONMENT))
 		return env_mmc_load_redundant();