drm/sti: use different notifier_block for each pipe

Each pipe shall have its own notifier block to manage the vblank event.
This fixes issues where a client registered on given pipe is later
abusively notified of events on the other pipe.

Signed-off-by: Fabien Dessenne <fabien.dessenne@st.com>
Acked-by: Vincent Abriou <vincent.abriou@st.com>
diff --git a/drivers/gpu/drm/sti/sti_compositor.h b/drivers/gpu/drm/sti/sti_compositor.h
index 24444ef..177c57b 100644
--- a/drivers/gpu/drm/sti/sti_compositor.h
+++ b/drivers/gpu/drm/sti/sti_compositor.h
@@ -62,7 +62,7 @@
  * @vid: array of vids
  * @vtg_main: vtg for main data path
  * @vtg_aux: vtg for auxillary data path
- * @vtg_vblank_nb: callback for VTG VSYNC notification
+ * @vtg_vblank_nb: array of callbacks for VTG VSYNC notification
  */
 struct sti_compositor {
 	struct device *dev;
@@ -78,7 +78,7 @@
 	struct sti_vid *vid[STI_MAX_VID];
 	struct sti_vtg *vtg_main;
 	struct sti_vtg *vtg_aux;
-	struct notifier_block vtg_vblank_nb;
+	struct notifier_block vtg_vblank_nb[STI_MAX_MIXER];
 };
 
 int sti_compositor_debufs_init(struct sti_compositor *compo,