Extcon: support generic GPIO extcon driver

The generic GPIO extcon driver (an external connector device based on
GPIO control) and imported from Android kernel.

switch: switch class and GPIO drivers. (splitted)
Author: Mike Lockwood <lockwood@android.com>

switch: gpio: Don't call request_irq with interrupts disabled
Author: Arve Hjønnevåg <arve@android.com>

switch_gpio: Add missing #include <linux/interrupt.h>
Author: Mike Lockwood <lockwood@android.com>

Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Reviewed-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

--
Changed from v7:
- Style updates mentioned by Stephen Boyd and Mark Brown
Changed from v5:
- Splitted at v5 from the main extcon patch.
- Added debounce time for irq handlers.
- Use request_any_context_irq instead of request_irq
- User needs to specify irq flags for GPIO interrupts (was fixed to
IRQF_TRIGGER_LOW before)
- Use module_platform_driver().
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/extcon/Kconfig

@@ -14,4 +14,11 @@ if EXTCON
 
 comment "Extcon Device Drivers"
 
+config EXTCON_GPIO
+	tristate "GPIO extcon support"
+	depends on GENERIC_GPIO
+	help
+	  Say Y here to enable GPIO based extcon support. Note that GPIO
+	  extcon supports single state per extcon instance.
+
 endif # MULTISTATE_SWITCH