gpio: Remove GPIO_DEVRES option

gpio: Remove GPIO_DEVRES option

This option was added in 0a918439ea2c11b5c374dcb9b8a888b25cfd9a07 to
allow use of the devm_gpio_* functions without CONFIG_GPIOLIB.

However, only a few months later in
96a6179b29dc7a57c4e8f935190fd0d6f2398013, 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
63384537cbca3dba19d862db857925e1aced6f45). 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>