drm/msm: Mark the crtc->state->event consumed

Don't leave the event != NULL once it's consumed, this is used a signal
to the atomic helpers that the event will be handled by the driver.

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

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

drivers/gpu/drm/msm/disp/mdp4/mdp4_crtc.c

@@ -351,6 +351,7 @@ static void mdp4_crtc_atomic_flush(struct drm_crtc *crtc,
 
 	spin_lock_irqsave(&dev->event_lock, flags);
 	mdp4_crtc->event = crtc->state->event;
+	crtc->state->event = NULL;
 	spin_unlock_irqrestore(&dev->event_lock, flags);
 
 	blend_setup(crtc);

drivers/gpu/drm/msm/disp/mdp5/mdp5_crtc.c

@@ -708,6 +708,7 @@ static void mdp5_crtc_atomic_flush(struct drm_crtc *crtc,
 
 	spin_lock_irqsave(&dev->event_lock, flags);
 	mdp5_crtc->event = crtc->state->event;
+	crtc->state->event = NULL;
 	spin_unlock_irqrestore(&dev->event_lock, flags);
 
 	/*