drm/drivers: add support for using the arch wc mapping API.

commit 7cf321d1 upstream.

This fixes a regression in all these drivers since the cache
mode tracking was fixed for mixed mappings. It uses the new
arch API to add the VRAM range to the PAT mapping tracking
tables.

Fixes: 87744ab3 (mm: fix cache mode tracking in vm_insert_mixed())
Reviewed-by: Christian König <christian.koenig@amd.com&gt;.>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Cc: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>