Revert radeon AGP aperture offset changes

Revert radeon AGP aperture offset changes

This reverts the series of commits

	7ebd3dd7afe5bac388e427a2ae957092b99ebc7f
	b18c7c26aae3a7782af7649357bf61f8ba5abe70
	89ac43b782b4103e1de8fdcf3ad7531b26584f4c

that changed the GART VM start offset.  It fixed some machines, but
seems to continually interact badly with some X versions.

Quoth Ben Herrenschmidt:

  "So I think at this point, the best is that we keep the old bogus code
   that at least is consistent with the bug in the server. I'm working on a
   big patch to X that reworks the memory map stuff completely and fixes
   those issues on the server side, I'll do a DRM patch matching this X fix
   as well so that the memory map is only ever set in one place and with
   what I hope is a correct algorithm..."

Signed-off-by: Linus Torvalds <torvalds@osdl.org>