gpio: mockup: add a dummy irqchip

Setup a dummy irqchip that will allow us to inject line events for
testing purposes.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index d4cec61..0504307 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -298,6 +298,8 @@
 	tristate "GPIO Testing Driver"
 	depends on GPIOLIB && SYSFS
 	select GPIO_SYSFS
+	select GPIOLIB_IRQCHIP
+	select IRQ_WORK
 	help
 	  This enables GPIO Testing driver, which provides a way to test GPIO
 	  subsystem through sysfs(or char device) and debugfs. GPIO_SYSFS