soc: qcom: pil: Use del_timer_sync() when cancelling notif timers

Currently, del_timer() is used to cancel the timers setup around
the notifications that are sent out during SSR. However,
del_timer() will only try to delete the timer if it is pending.
In cases where the timer is no longer pending because it is
being expired, del_timer() will return immediately, and the
SSR call flow will continue, which is not correct, because at
that point, SSR has taken too long, and the timer handler will
soon crash the system.

Use del_timer_sync() on the timers used for SSR
notification timeouts to wait for the timer to be expired
completely, if it is expiring, to ensure that we only
continue with SSR if the timer did not expire at all.

Change-Id: Ib9570aeb1532e6012a36c29376bfb779a8505baf
Signed-off-by: Isaac J. Manjarres <isaacm@codeaurora.org>