viafb: Add OLPC XO-1.5 port configs

The OLPC XO-1.5 does not use the standard port wiring suggested
in the viafb driver.

This is required for the upcoming OLPC DCON and via-camera drivers,
to be submitted soon.

Signed-off-by: Daniel Drake <dsd@laptop.org>
[fts: removed useless ifdef's and corrected comment]
Signed-off-by: Florian Tobias Schandinat <FlorianSchandinat@gmx.de>