Right now its the only VIA AGP 3.0 chipset. At some point in
time it may become via-agp3.c, but until then its cleaner to
seperate this from the VIA AGP 2.0 driver.

The 2.0 driver will still work on a KT400 with a 2.0 compliant graphic
card present. If the 2.0 driver finds the bridge in 3.0 mode, it aborts.
Likewise, the 3.0 driver will abort if the bridge is in 2.0 mode.

Confused yet?