drm: update PCIGART support from CVS

In order to work on FreeBSD the gart needed to use a local mapping
This patch moves the mainline to the new code and aligns some comment
changes

From: Eric Anholt <anholt@freebsd.org>
Signed-off-by: Dave Airlie <airlied@linux.ie>
diff --git a/drivers/char/drm/r128_irq.c b/drivers/char/drm/r128_irq.c
index 27eb0e3..87f8ca2 100644
--- a/drivers/char/drm/r128_irq.c
+++ b/drivers/char/drm/r128_irq.c
@@ -1,5 +1,5 @@
-/* r128_irq.c -- IRQ handling for radeon -*- linux-c -*-
- *
+/* r128_irq.c -- IRQ handling for radeon -*- linux-c -*- */
+/*
  * Copyright (C) The Weather Channel, Inc.  2002.  All Rights Reserved.
  *
  * The Weather Channel (TM) funded Tungsten Graphics to develop the