drm/nouveau: add NV18 device id to call_lvds_manufacturer_script

This fixes imac black screen (NV18 card)

Signed-off-by: Andrea Tacconi <tacconet@libero.it>
Signed-off-by: Francisco Jerez <currojerez@riseup.net>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>