drm: Create drm_send_event helpers

Use them in the core vblank code and exynos/vmwgfx drivers.

Note that the difference between wake_up_all and _interruptible in
vmwgfx doesn't matter since the only waiter is the core code in
drm_fops.c. And that is interruptible.

v2: Adjust existing kerneldoc too.

Reviewed-by: Alex Deucher <alexander.deucher@amd.com> (v1)
Acked-by: Daniel Stone <daniels@collabora.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Thomas Hellstrom <thellstrom@vmware.com>
Cc: Inki Dae <inki.dae@samsung.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1452548477-15905-6-git-send-email-daniel.vetter@ffwll.ch
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
[danvet: Squash in compile fixup, spotted by 0-day.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/drm_irq.c

@@ -983,15 +983,12 @@ static void send_vblank_event(struct drm_device *dev,
 		struct drm_pending_vblank_event *e,
 		unsigned long seq, struct timeval *now)
 {
-	assert_spin_locked(&dev->event_lock);
-
 	e->event.sequence = seq;
 	e->event.tv_sec = now->tv_sec;
 	e->event.tv_usec = now->tv_usec;
 
-	list_add_tail(&e->base.link,
-		      &e->base.file_priv->event_list);
-	wake_up_interruptible(&e->base.file_priv->event_wait);
+	drm_send_event_locked(dev, &e->base);
+
 	trace_drm_vblank_event_delivered(e->base.pid, e->pipe,
 					 e->event.sequence);
 }