drm: small fix in drm_send_vblank_event()

Initialize e->pipe.. some drivers set this themselves, others do not.
Setting it in drm_send_vblank_event() should help ensure more consistent
behavior with the different drivers.

Signed-off-by: Rob Clark <robdclark@gmail.com>
diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
index 38e7992..a6a8643 100644
--- a/drivers/gpu/drm/drm_irq.c
+++ b/drivers/gpu/drm/drm_irq.c
@@ -867,6 +867,7 @@
 
 		now = get_drm_timestamp();
 	}
+	e->pipe = crtc;
 	send_vblank_event(dev, e, seq, &now);
 }
 EXPORT_SYMBOL(drm_send_vblank_event);