drm/ttm: stop exporting ttm_mem_io_* functions

Those are not supposed to be used by drivers.

Signed-off-by: Christian König <christian.koenig@amd.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Link: https://patchwork.freedesktop.org/patch/333290/
1 file changed