amd64-agp: fix crash at second module load

The module forgot to sometimes unregister some resources.

This fixes Bug #22882.

[Patch updated to 2.6.38-rc3 by Randy Dunlap.]
Tested-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Florian Mickler <florian@mickler.org>
Signed-off-by: Dave Airlie <airlied@redhat.com>