s3fb: Add Virge/MX (86C260)

Add support for Virge/MX (86C260) chip. Although this is a laptop chip,
there's an AGP card with this chip too.

Tested with AGP card, will probably not work correctly with laptops.
DDC does not work on this card (even in DOS or Windows).

Signed-off-by: Ondrej Zary <linux@rainbow-software.org>
Signed-off-by: Florian Tobias Schandinat <FlorianSchandinat@gmx.de>