gpio: sch: Add edge event support

Add the required infrastructure to enable and report edge events
of the pins to the GPIO core. The actual hook-up of the event interrupt
will happen separately.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Co-developed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index 6fb13d6..ad1a325 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -861,6 +861,7 @@
 config GPIO_SCH
 	tristate "Intel SCH/TunnelCreek/Centerton/Quark X1000 GPIO"
 	depends on (X86 || COMPILE_TEST) && PCI
+	select GPIOLIB_IRQCHIP
 	select MFD_CORE
 	select LPC_SCH
 	help