gpio: msc313: Code clean ups

- Remove the unneeded assignment of ret before returning it.
- Remove an unneeded blank line

Signed-off-by: Daniel Palmer <daniel@0x0f.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>