msm: cpp: Synchronize tasklet and timeout work queue

CPP driver times out for a particular frame. Interrupt for a
particular frame is received after timeout. Tasklet is initiated
but not scheduled. Timeout sequence reloads the firmware. Before
frame is rescheduled from timeout, tasklet is scheduled and
frame is removed from queue. Null pointer dereference occurs when
timeout tries to schedule a frame that is removed from queue.

Ensure any pending scheduled events on tasklet is executed before
time out sequence reload firmware and reschedules the frame.

CRs-Fixed: 928854
Change-Id: I6b6fb55fcdfea936456ad1dd81082f19b3825c9c
Signed-off-by: Krishnankutty Kolathappilly <kkolatha@codeaurora.org>