gpio: fix SNPS_CREG kconfig dependency warning

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>

drivers/gpio/Kconfig

@@ -440,7 +440,7 @@ config GPIO_SIOX
 config GPIO_SNPS_CREG
 	bool "Synopsys GPIO via CREG (Control REGisters) driver"
 	depends on ARC || COMPILE_TEST
-	select OF_GPIO
+	depends on OF_GPIO
 	help
 	  This driver supports GPIOs via CREG on various Synopsys SoCs.
 	  This is a single-register MMIO GPIO driver for complex cases