msm: mdss: ensure pipe is halted before freeing buffers

When pipe is being detached from mixer, there is potential corner case
if underrun occurs at the same time which can cause pipe to flood the
VBIF. On the other hand unmapping a buffer requires VBIF to be idle to
sync TLB, so need to ensure pipe halt is done before freeing the pipe
buffers.

Change-Id: I9686b9d7d17d8dc2a8334157cfa8fa23ba5b47ee
Signed-off-by: Adrian Salido-Moreno <adrianm@codeaurora.org>
msm: mdss: Handle case when pipe is not idle during cleanup.

When pipe is not idle during cleanup, MDP can go into an unrecoverable
state, which can lead into other issues. If it gets to this point we
need to recover even if it means changing display contents for a
fraction of time. To handle this follow recovery sequence:
1. Setup the pipes that are not idle to solid fill mode so that nothing
   is fetched from memory on these pipes.
2. Stage them into mixer, flush and wait for a vsync to happen and reset
   sequence to take effect on these.
3. Finally, reattach the current frame pipes to restore display back to
   normal.

Change-Id: If545b56bf32a46699871381d86e80c1980ec3cc7
Signed-off-by: Jayant Shekhar <jshekhar@codeaurora.org>
Signed-off-by: Adrian Salido-Moreno <adrianm@codeaurora.org>

Conflicts:
	drivers/video/msm/mdss/mdss_mdp_overlay.c