drivers: gpio: Add driver for smartbond

This adds GPIO driver for Renesas SmartBond(tm) family.

Driver supports pin configuration (input/output) and interrupts on edge.
Interrupts on level are not supported by hardware.

Signed-off-by: Andrzej Kaczmarek <andrzej.kaczmarek@codecoup.pl>
Signed-off-by: Ben Lauret <ben.lauret.wm@renesas.com>