gpio-f7188x: Add GPIO support for F81865

Add GPIO support for Fintek F81865 chip.

Datasheet: http://www.hardwaresecrets.com/datasheets/F81865_V028P.pdf



Signed-off-by: Petteri Jokinen <petteri@kiho.fi>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>