gpio: move Nomadik GPIO driver to drivers/gpio

This moves the Nomadik GPIO driver out of arch/arm/plat-nomadik
and into the desired location indicated by the subsystem
maintainer.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
[grant.likely: squashed with kconfig fixup]
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>