soc: qcom: Add snapshot of watchdog_v2 driver

This is a snapshot of the watchdog_v2 driver as of msm-4.9
commit '1a00b60049366e3f717973040f5f97ed9b972c10'. ("Update
last_pet variable during resume") The last_pet variable is
set in suspend callback and during pet_watchdog() and is
printed when watchdog bark handler gets called. This variable
does not represent exact last pet time in cases where non secure
bark occurs before system could pet the watchdog upon wakeup
event from low power mode. Reset the watchdog during
msm_watchdog_resume() and update last_pet variable so that
watchdog bark messages will represent latest info.

This commit also adds memory barrier after resetting watchdog in
msm_watchdog_suspend(). This will make sure watchdog writes are
complete before proceeding further.

Change-Id: I50190aa37c06bac21e91450d33312139ee532109
Signed-off-by: Rama Aparna Mallavarapu <aparnam@codeaurora.org>