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

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