disp: msm: sde: wait for pending crtcs before lastclose commits

If a SIG_TERM/SIG_KILL or other signal is sent to the final drm
client, the driver will be force-closed. A -ERESTARTSYS error is
occasionally seen from the interruptible wait in
msm_atomic_commit when this occurs, and causes the lastclose
cleanup to fail if any crtc is busy at that point. To prevent
this, wait for any pending crtcs to complete before calling
the lastclose cleanup commits.

Change-Id: Ib6a5e55a4b737213756cb9ed8364d5c34ab47c16
Signed-off-by: Steve Cohen <cohens@codeaurora.org>