soc: qcom: Add watchdog bite in panic

Add watchdog bite in panic by registering a restart handler. Also add
support for an earlier watchdog bite in the panic handler itself, which
should provide a better context for post-mortem analysis.

Change-Id: Ib6530fa754b78fd26a9f7d5a348b1e7ceb3c1f96
Signed-off-by: Elliot Berman <eberman@codeaurora.org>