The declaration of U_BOOT_ENV_LOCATION() uses a different #ifdef
condition from the code it calls. Use the same condition to avoid a
build warning if CONFIG_CMD_SAVEENV is disabled.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>