drm/i915: Add ACPI OpRegion support for Ironlake

Add the support of ACPI opregion on Ironlake so that the backlight
brightness can be adjusted by using ACPI interface
   >/sys/class/backlight/acpi_video0/brightness

Signed-off-by: Zhao Yakui <yakui.zhao@intel.com>
Tested-by: Zhao Yakui <yakui.zhao@intel.com>
[zhenyuw: cleanups, fix typo for checking GSE irq and convert to
current irq handling logic.]
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>
Signed-off-by: Eric Anholt <eric@anholt.net>
diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
index 794ded2..093146b 100644
--- a/drivers/gpu/drm/i915/i915_dma.c
+++ b/drivers/gpu/drm/i915/i915_dma.c
@@ -1492,9 +1492,7 @@
 	}
 
 	/* Must be done after probing outputs */
-	/* FIXME: verify on IGDNG */
-	if (!IS_IGDNG(dev))
-		intel_opregion_init(dev, 0);
+	intel_opregion_init(dev, 0);
 
 	setup_timer(&dev_priv->hangcheck_timer, i915_hangcheck_elapsed,
 		    (unsigned long) dev);
@@ -1538,8 +1536,7 @@
 	if (dev_priv->regs != NULL)
 		iounmap(dev_priv->regs);
 
-	if (!IS_IGDNG(dev))
-		intel_opregion_free(dev, 0);
+	intel_opregion_free(dev, 0);
 
 	if (drm_core_check_feature(dev, DRIVER_MODESET)) {
 		intel_modeset_cleanup(dev);