drm/i915: Use consistent mappings for OpRegion between ACPI and i915

The opregion is a shared memory region between ACPI and the graphics
driver. As the ACPI mapping has been changed to cachable in commit
6d5bbf00, mapping the intel opregion
non-cachable now fails. As no bus-master hardware is involved in the
opregion, cachable map should do no harm.

Tested on a Fujitsu Lifebook P8010.
Signed-off-by: Michael Karcher <kernel@mkarcher.dialup.fu-berlin.de>
[ickle: convert to acpi_os_ioremap for consistency]
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

drivers/gpu/drm/i915/intel_opregion.c

@@ -26,6 +26,7 @@
  */
 
 #include <linux/acpi.h>
+#include <linux/acpi_io.h>
 #include <acpi/video.h>
 
 #include "drmP.h"
@@ -476,7 +477,7 @@ int intel_opregion_setup(struct drm_device *dev)
 		return -ENOTSUPP;
 	}
 
-	base = ioremap(asls, OPREGION_SIZE);
+	base = acpi_os_ioremap(asls, OPREGION_SIZE);
 	if (!base)
 		return -ENOMEM;