gpio: enable callback to specify pin in addition to pin_mask
gpio: enable callback to specify pin in addition to pin_mask

There are GPIO controllers that can control more than 32 pins.
The pin_mask is no longer adequate in this case. This wraps
the pin_mask in a union together with a field named 'pin'.
The driver is responsible for choosing whether to use
pin_mask or pin.

Signed-off-by: Daniel Leung <d94e04d205b5962d7873a139ef298b03c1717f72@intel.com>

explora26/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,kraj/zephyr,galak/zephyr,finikorg/zephyr,kraj/zephyr,GiulianoFranchetto/zephyr,Vudentz/zephyr,ldts/zephyr,kraj/zephyr,galak/zephyr,explora26/zephyr,punitvara/zephyr,galak/zephyr,punitvara/zephyr,nashif/zephyr,ldts/zephyr,nashif/zephyr,finikorg/zephyr,explora26/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,galak/zephyr,kraj/zephyr,nashif/zephyr,galak/zephyr,nashif/zephyr,GiulianoFranchetto/zephyr,nashif/zephyr,punitvara/zephyr,GiulianoFranchetto/zephyr,Vudentz/zephyr,punitvara/zephyr,ldts/zephyr,punitvara/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,GiulianoFranchetto/zephyr,ldts/zephyr,explora26/zephyr,GiulianoFranchetto/zephyr,kraj/zephyr,Vudentz/zephyr,explora26/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,finikorg/zephyr,ldts/zephyr