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/drm_memory.c b/drivers/gpu/drm/drm_memory.c
index 803bc9e..bcc869b 100644
--- a/drivers/gpu/drm/drm_memory.c
+++ b/drivers/gpu/drm/drm_memory.c
@@ -171,9 +171,14 @@
 
 void drm_core_ioremap_wc(struct drm_map *map, struct drm_device *dev)
 {
-	map->handle = ioremap_wc(map->offset, map->size);
+	if (drm_core_has_AGP(dev) &&
+	    dev->agp && dev->agp->cant_use_aperture && map->type == _DRM_AGP)
+		map->handle = agp_remap(map->offset, map->size, dev);
+	else
+		map->handle = ioremap_wc(map->offset, map->size);
 }
 EXPORT_SYMBOL(drm_core_ioremap_wc);
+
 void drm_core_ioremapfree(struct drm_map *map, struct drm_device *dev)
 {
 	if (!map->handle || !map->size)