drm/i915: call ibx_irq_uninstall from gen8_irq_uninstall

After all, we call ibx_irq_preinstall from gen8_irq_preinstall.

v2: - Rebase.
Reviewed-by: NBen Widawsky <ben@bwidawsk.net>
Signed-off-by: NPaulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_irq.c

@@ -3310,6 +3310,8 @@ static void gen8_irq_uninstall(struct drm_device *dev)
 	GEN5_IRQ_RESET(GEN8_DE_PORT_);
 	GEN5_IRQ_RESET(GEN8_DE_MISC_);
 	GEN5_IRQ_RESET(GEN8_PCU_);
+
+	ibx_irq_uninstall(dev);
 }
 
 static void valleyview_irq_uninstall(struct drm_device *dev)