If enabled, during initialization BO GTT->VRAM and VRAM->GTT GPU copies are
tested across the whole GTT aperture.

This has helped uncover the benchmark copy size bug and verify the maximum
aperture size supported by the AGP bridge in my PowerBook.
Signed-off-by: Michel Dänzer <daenzer@vmware.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>