soc: qcom: watchdog_v2: Support userspace watchdog

Provide a hw guarantee that a userspace watchdog process receives cpu time.
Move ping_other_cpus() prior to waiting for the userspace signal in order
to minimize the effect of a late userspace pet on the safety margin.  The
safety margin is the difference between the workqueue's timer interval and
the bite interval.

Change-Id: I715cf7ad7975c6e020458f623262dc02927795a7
Signed-off-by: Patrick Daly <pdaly@codeaurora.org>