msm: mhi: Queue pending_ring WQ post channel DB check

Change is to queue pending_ring post updating CH db_pend
variable. This is done to avoid chdb_ctrl_work WQ from getting
pre-empted and pending_ring WQ executing.

Change-Id: I3504c89006c1231251be6efdfebac52b0fd35cc9
Signed-off-by: Subramanian Ananthanarayanan <skananth@codeaurora.org>
Signed-off-by: Gauri Joshi <gaurjosh@codeaurora.org>