gxfb: use PCI_DEVICE() for gxfb's pci device table

Drop the class/class_mask stuff; it's unnecessary as long as the vendor and
device IDs match.

Signed-off-by: Andres Salomon <dilinger@debian.org>
Cc: "Antonino A. Daplas" <adaplas@pol.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>