gpio: Remove GPIO_DEVRES option

gpio: Remove GPIO_DEVRES option

This option was added in 77a67b4a31447d4159072258c80a0c420d8b6cc5 to
allow use of the devm_gpio_* functions without CONFIG_GPIOLIB.

However, only a few months later in
0f54a6f10cd1928b44c898ff13293165aa347107, CONFIG_GPIOLIB was added
as a dependency, defeating the original purpose of this option.
Instead of that patch, the original commit could have just been
reverted (and in fact was partially so in
97fbfaa2f29d991509b2b92d0fcaa48f6d05804e). Further, since this
option has a dependency on HAS_IOMEM, even though it does not
require it, it causes build failures when !HAS_IOMEM (e.g. in a
uml build).

Fix that by completely removing the option, in essence completing
the reversion of the original commit.

Signed-off-by: Keno Fischer <keno@juliacomputing.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>