gpio: delete ARCH_[WANTS_OPTIONAL|REQUIRE]_GPIOLIB

The GPIOLIB is now selectable explicitly, and always available
for all archs. All archs that require GPIOLIB are switched to
select GPIOLIB directly. Delete the hairy ARCH_REQUIRE_GPIOLIB
and ARCH_WANTS_OPTIONAL_GPIOLIB Kconfig symbols.

Cc: Michael Büsch <m@bues.ch>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>