drm/i915: vlv: keep first level vblank IRQs masked

This is a left-over from

commit b7e634cc8dcd320123199a18bae0937b40dc28b8
Author: Imre Deak <imre.deak@intel.com>
Date:   Tue Feb 4 21:35:45 2014 +0200

drm/i915: vlv: don't unmask IIR[DISPLAY_PIPE_A/B_VBLANK] interrupt

where we stopped unmasking the vblank IRQs, but left them enabled in the
IER register. Disable them in IER too.

v2:
- remove comment becoming stale after this change (Ville)

Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_irq.c

@@ -3035,17 +3035,9 @@ static int valleyview_irq_postinstall(struct drm_device *dev)
 
 	enable_mask = I915_DISPLAY_PORT_INTERRUPT;
 	enable_mask |= I915_DISPLAY_PIPE_A_EVENT_INTERRUPT |
-		I915_DISPLAY_PIPE_A_VBLANK_INTERRUPT |
-		I915_DISPLAY_PIPE_B_EVENT_INTERRUPT |
-		I915_DISPLAY_PIPE_B_VBLANK_INTERRUPT;
+		I915_DISPLAY_PIPE_B_EVENT_INTERRUPT;
 
-	/*
-	 *Leave vblank interrupts masked initially.  enable/disable will
-	 * toggle them based on usage.
-	 */
-	dev_priv->irq_mask = (~enable_mask) |
-		I915_DISPLAY_PIPE_A_VBLANK_INTERRUPT |
-		I915_DISPLAY_PIPE_B_VBLANK_INTERRUPT;
+	dev_priv->irq_mask = ~enable_mask;
 
 	I915_WRITE(PORT_HOTPLUG_EN, 0);
 	POSTING_READ(PORT_HOTPLUG_EN);