drm/nouveau: fix multihop when move doesn't work.

As per the radeon/amdgpu fix don't use multihop if hw moves
aren't enabled.

Reported-by: Mike Galbraith <efault@gmx.de>
Tested-by: Mike Galbraith <efault@gmx.de>
Fixes: 0c8c0659 ("drm/nouveau/ttm: use multihop")
Signed-off-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20201217200943.30511-1-airlied@gmail.com