drm/msm: Issue queued events when disabling crtc

Ensure that any queued events are issued when disabling the crtc. This
avoids timeouts when we come back and wait for dependencies (like the
previous frame's flip_done).

Changes in v2:
- None
Changes in v3:
- Rebased on Archit's private_obj set
Changes in v4:
- None

Reviewed-by: Archit Taneja <architt@codeaurora.org>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Signed-off-by: Rob Clark <robdclark@gmail.com>