msm: qpnp-power-on: add support for handling pmic watchdog barks

PMIC watchdog resets are often very difficult to debug due to the sudden
shutdown of the system. Add support in the qpnp-power-on driver to
handle the pmic watch dog bark, log a message and panic so that the
reset reason is clear to testers.

Change-Id: I0b7f3f3780769a8260cce73ee8dce91200e8873a
Signed-off-by: Xiaozhe Shi <xiaozhes@codeaurora.org>