drm/nouveau: match U/DP script against SOR link

It appears version 0x21 'U' and 'd' tables require us to take the SOR link
into account when selecting the appropriate table for a particular output.

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>