msm_fb: display: fix iommu page fault when iommu buffer freed

There has possibility that pipe commit come very close to next vsync.
This may cause two consecutive pipe_commits happen within same vsync
period which cause iommu page fault when previous iommu buffer is
freed since mdp stil fetching it. Set ION_IOMMU_UNMAP_DELAYED flag
at ion_map_iommu() to add delay un mapping iommu buffer to fix this problem.
Otherwise four buffer mechanism is needed to avoid this problem..
Also ion_unmap_iommu() may take long time to free an ion buffer. Move
mdp4_overlay_iommu_unmap_freelist(mixer) called after stage_commit()
to increase chance to have pipe_commit (up to stage_commit) is completed
within same vsync period
This patch also fix an potential race condition at wait_for_completion
between show_event thread and wait4vsync thread.

Change-Id: I089950ac61c0bd3c4207b8925817577e42fbb258
Signed-off-by: Kuogee Hsieh <khsieh@codeaurora.org>
msm: display: Fix composition issues when framework rebooted in suspend.

Currently, if framework is rebooted while in suspend mode, borderfill
is not unset due to which MDP composition can not be enabled. This patch
fixes the issue.

Change-Id: I8b671eccedebf2bb08724cf2d284d4ab27a71360
Signed-off-by: Vishnuvardhan Prodduturi <vproddut@codeaurora.org>