power: reset: msm: Handle dm-verity and keys reset reasons

Write magic cookies/PON reset reason to indicate reasons
of dm-verity corruption, re-enable enforcing mode, and
(unrelated) keys clear.

Change-Id: I49904c79940515863d794b23fa7ac84e472b2466
Signed-off-by: David Ng <dave@codeaurora.org>