arm64: do away with ARCH_[WANT_OPTIONAL|REQUIRE]_GPIOLIB

This replaces:

- "select ARCH_REQUIRE_GPIOLIB" with "select GPIOLIB" as this can
  now be selected directly.

- "select ARCH_WANT_OPTIONAL_GPIOLIB" with no dependency: GPIOLIB
  is now selectable by everyone, so we need not declare our
  intent to select it.

Cc: Michael Büsch <m@bues.ch>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>