gpio: ucb1400: Add MODULE_ALIAS

This driver can be built as a module now.
Add MODULE_ALIAS to support module auto-loading.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Reviewed-by: Jean Delvare <jdelvare@suse.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>