drm/i915: Silence an innocuous compiler warning for an unused variable

drivers/gpu/drm/i915/i915_irq.c: In function ‘ironlake_irq_postinstall’:
drivers/gpu/drm/i915/i915_irq.c:1618: warning: unused variable ‘pipe’
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

drivers/gpu/drm/i915/i915_irq.c

@@ -1615,7 +1615,6 @@ static int ironlake_irq_postinstall(struct drm_device *dev)
 			   DE_PLANEA_FLIP_DONE | DE_PLANEB_FLIP_DONE;
 	u32 render_irqs;
 	u32 hotplug_mask;
-	int pipe;
 
 	dev_priv->irq_mask = ~display_mask;