gpio: remove deps on ARCH_[WANT_OPTIONAL|REQUIRE]_GPIOLIB

The GPIOLIB symbol currently require that
ARCH_WANT_OPTIONAL_GPIOLIB or ARCH_REQUIRE_GPIOLIB is selected
to be selectable.

The ARCH_REQUIRE_GPIOLIB does only one thing: select GPIOLIB.

This is just confusing: architectures that want GPIOLIB should
be able to configure it in no matter what, and those who
require it should just select GPIOLIB.

It also creates problems for drivers that need to state
"select GPIOLIB" to get dependencies: those depend on the
selected architecture to select
ARCH_[WANT_OPTIONAL|REQUIRE]_GPIOLIB first, and will cause
compile errors for the few archs that state neither.

These intermediary symbols need to go.

As a first step, remove the dependencies so that:

- ARCH_WANT_OPTIONAL_GPIOLIB becomes a noop (GPIOLIB will be
  available for everyone) and

- "select ARCH_REQUIRE_GPIOLIB" can be replaced by just
  "select GPIOLIB"

After this patch we can follow up with patches cleaning up the
architectures one-by one and eventually remove the
ARCH_[WANT_OPTIONAL|REQUIRE]_GPIOLIB symbols altogether.

Reported-by: Michael Hennerich <michael.hennerich@analog.com>
Cc: Michael Büsch <m@bues.ch>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>