We need it for PFIFO_INTR_CACHE_ERROR interrupt handling,
because nouveau_fifo_swmthd looks for matching gpuobj in
ramht_refs list.
It fixes kernel panic in nouveau_gpuobj_ref_find.
Signed-off-by: NMarcin Slusarz <marcin.slusarz@gmail.com>
Signed-off-by: NBen Skeggs <bskeggs@redhat.com>