disp: msm: sde: cache encoder_mask for vblank_work

There is a race between disable commit swap-state on display
thread and vblank work on event thread which may skip applying
the vblank vote if the encoder_mask has already been cleared.
To avoid the race, use a cached encoder_mask that is gauranteed
to be valid between the vblank_on and vblank_off calls.

Also, vblank queue work is initializing a variable that's never
used and msm_disable_outputs has 2 instances of pointers to old
CRTC state. Remove this dead code.

Change-Id: I5e4a482b8f067e272a2aef5afa08cc0e1ab89434
Signed-off-by: Steve Cohen <cohens@codeaurora.org>

msm/msm_drv.c

@@ -366,7 +366,6 @@ static int vblank_ctrl_queue_work(struct msm_drm_private *priv,
 					int crtc_id, bool enable)
 {
 	struct vblank_work *cur_work;
-	struct drm_crtc *crtc;
 	struct kthread_worker *worker;
 
 	if (!priv || crtc_id >= priv->num_crtcs)
@@ -376,8 +375,6 @@ static int vblank_ctrl_queue_work(struct msm_drm_private *priv,
 	if (!cur_work)
 		return -ENOMEM;
 
-	crtc = priv->crtcs[crtc_id];
-
 	kthread_init_work(&cur_work->work, vblank_ctrl_worker);
 	cur_work->crtc_id = crtc_id;
 	cur_work->enable = enable;