staging: greybus: gpio: it's CONFIG_GPIOLIB, not CONFIG_GPIO

The GPIO dependancy is CONFIG_GPIOLIB, not CONFIG_GPIO, no wonder it
wasn't building properly...
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

drivers/staging/greybus/Kconfig

@@ -147,7 +147,7 @@ if GREYBUS_BRIDGED_PHY
 
 config GREYBUS_GPIO
 	tristate "Greybus GPIO Bridged PHY driver"
-	depends on GPIO
+	depends on GPIOLIB
 	---help---
 	  Select this option if you have a device that follows the
 	  Greybus GPIO Bridged PHY Class specification.