sil164 transmitters are used for DVI outputs on Intel/nvidia and ATI setups.

So far only nouveau can use this driver.
Signed-off-by: NFrancisco Jerez <currojerez@riseup.net>
Tested-by: NPatrice Mandin <patmandin@gmail.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>