regulator: gpio-regulator add dependency on GENERIC_GPIO

Without GENERIC_GPIO "struct gpio" is undefined leading to errors.
Reported-by: Randy Dunlap <rdunlap@xenotime.net>
Acked-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

drivers/regulator/Kconfig

@@ -66,6 +66,7 @@ config REGULATOR_USERSPACE_CONSUMER
 
 config REGULATOR_GPIO
 	tristate "GPIO regulator support"
+	depends on GENERIC_GPIO
 	help
 	  This driver provides support for regulators that can be
 	  controlled via gpios.