msm_fb: display: clean pipes from commit queue at suspend

There has possibility that pipes pending at queue and suspend
comes without commit executed. At resume, pipes pending at queue
will be committed with new pipes just added which may cause iommu
page fault due to pipes may had been move to other mixer. This
patch remove pipes from pending queue at suspend.

CRs-fixed: 440254
Change-Id: If6a142d4c55453c0ceacc677399f58570abe47b8
Signed-off-by: Kuogee Hsieh <khsieh@codeaurora.org>