drm/radeon: fix ioremap conflict with AGP mappings

this solves a regression from
http://bugzilla.kernel.org/show_bug.cgi?id=12441

Reported-by: Daniel Vetter <daniel@ffwll.ch>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/radeon/radeon_cp.c b/drivers/gpu/drm/radeon/radeon_cp.c
index 63212d7..df4cf97 100644
--- a/drivers/gpu/drm/radeon/radeon_cp.c
+++ b/drivers/gpu/drm/radeon/radeon_cp.c
@@ -1039,9 +1039,9 @@
 
 #if __OS_HAS_AGP
 	if (dev_priv->flags & RADEON_IS_AGP) {
-		drm_core_ioremap(dev_priv->cp_ring, dev);
-		drm_core_ioremap(dev_priv->ring_rptr, dev);
-		drm_core_ioremap(dev->agp_buffer_map, dev);
+		drm_core_ioremap_wc(dev_priv->cp_ring, dev);
+		drm_core_ioremap_wc(dev_priv->ring_rptr, dev);
+		drm_core_ioremap_wc(dev->agp_buffer_map, dev);
 		if (!dev_priv->cp_ring->handle ||
 		    !dev_priv->ring_rptr->handle ||
 		    !dev->agp_buffer_map->handle) {