drivers: power: Add watchdog timer to catch drivers which lockup during suspend.

drivers: power: Add watchdog timer to catch drivers which lockup during suspend.

Rather than hard-lock the kernel, dump the suspend thread stack and
BUG() when a driver takes too long to suspend.  The timeout is set
to 12 seconds to be longer than the usbhid 10 second timeout.

Exclude from the watchdog the time spent waiting for children that
are resumed asynchronously and time every device, whether or not they
resumed synchronously.

Change-Id: Ifd211c06b104860c2fee6eecfe0d61774aa4508a
Original-author: San Mehat <san@google.com>
Signed-off-by: Benoit Goby <benoit@android.com>