Input: sirfsoc-onkey - report release event by detecting pin status

This change adds a delayed_work to detect the release of onkey since HW will
not generate interrupt for it.

At the same time, we move the KEY event to POWER instead of SUSPEND, which
will be suitable for both Android and Linux. Userspace PowerManager Daemon
will decide to suspend or shutdown based on how long we have touched onkey.

Signed-off-by: Xianglong Du <Xianglong.Du@csr.com>
Signed-off-by: Rongjun Ying <Rongjun.Ying@csr.com>
Signed-off-by: Barry Song <Baohua.Song@csr.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>