The sama5d2 features a GPIO and pin controller different than the one
we support in barebox. The device tree bindings are different as well,
so it makes sense to have a separate driver for it.

Add the pin control and GPIO driver as well as some helpers usable
from PBL, should we want to do pinmuxing that early.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>