Remove "switch" class in drivers/staging/android/switch

Because extcon can also be a switch class for legacy userspace (Android)
and is a superset of switch class in drivers/staging/android/switch,
switch class may be removed.

- Remove switch class
- Remove switch class consideration in extcon class

Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>