viafb: fix OLPC XO 1.5 device connection

This patch fixes the devices connected on OLPC. The OLPC panel seems
to be connected to DVP1 and LVDS2 for some reasons and if not both
are handled correct the display does not work correct or not at all.
This patch prevents regressions on the OLPC where it worked by
accident but would break in future as the driver did not know the
correct devices connected. This might also fix hardware scaling.
Hopefully the OLPC is the only device with such a requirement but it
will be certainly better to actually know what devices are actually
connected and to not work by accident.

Signed-off-by: Florian Tobias Schandinat <FlorianSchandinat@gmx.de>