drm/radeon: fixup issue with radeon and PAT support.

With new userspace libpciaccess we can get a conflicting mapping
on the PCIE GART table in the video RAM. Always try and map it _wc.

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 e53158f..f0de81a 100644
--- a/drivers/gpu/drm/radeon/radeon_cp.c
+++ b/drivers/gpu/drm/radeon/radeon_cp.c
@@ -1154,7 +1154,7 @@
 			dev_priv->gart_info.mapping.size =
 			    dev_priv->gart_info.table_size;
 
-			drm_core_ioremap(&dev_priv->gart_info.mapping, dev);
+			drm_core_ioremap_wc(&dev_priv->gart_info.mapping, dev);
 			dev_priv->gart_info.addr =
 			    dev_priv->gart_info.mapping.handle;