gpio: Fix up merge collision in include file

The merge of two different patch sets cleaning around in the
main driver include file collided making the function
declarations for gpiochip_[un]lock_as_irq() be defined twice
when gpiolib was unselected. Fix it up.

Cc: YueHaibing <yuehaibing@huawei.com>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>