Fix kconfig warning for GPIO_SNPS_CREG:

WARNING: unmet direct dependencies detected for OF_GPIO
  Depends on [n]: GPIOLIB [=y] && OF [=n] && HAS_IOMEM [=y]
  Selected by [y]:
  - GPIO_SNPS_CREG [=y] && GPIOLIB [=y] && HAS_IOMEM [=y] && (ARC || COMPILE_TEST [=y])

Drivers in drivers/gpio/Kconfig depend on OF_GPIO, not select it.
This prevents attempting to build when OF is not enabled.

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: linux-gpio@vger.kernel.org
Cc: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>