drm: rationalise some pci ids

This is the start of some work from Roland Scheidegger to align
the X DDX pci ids and the drm ones, however we don't want to put
r300 ids in the kernel just yet, they destabilise a few machines.

From: Roland Scheidegger (via DRM CVS)
Signed-off-by: Dave Airlie <airlied@linux.ie>