radeon,r200: remove support for UMS radeon DRM module

radeon,r200: remove support for UMS radeon DRM module

As mentioned by Michel Dänzer
 "FWIW though, any code which is specific to radeon DRM major version 1
  can be removed, because that's the UMS major version."

and Marek Olšák
 "major != 2" can't occur. You don't have to check the major version at
  all and you can just assume it's always 2."

Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Reviewed-by: Michel Dänzer <michel.daenzer@amd.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>