soc/intel/apollolake: Add function to translate gpio_t into ACPI pin

soc/intel/apollolake: Add function to translate gpio_t into ACPI pin

There are four GPIO communities in this SOC and they are implemented
as separate ACPI devices.  This means the pin number that is used in
an ACPI GPIO declaration needs to be relative to the community that
the pin resides in.  Also select GENERIC_GPIO_LIB in the SOC Kconfig
so this function actually gets used.

This was tested on the reef mainboard by verifying the output of the
SSDT for the Maxim 98357A codec that the assigned GPIO_76 is listed
as pin 0x24 which is the value relative to the Northwest community.

Change-Id: Iad2ab8eccf4c91185a075ffce8d41c81f06c1113
Signed-off-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-on: https://review.coreboot.org/15513
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Tested-by: build bot (Jenkins)