drm/radeon: switch r6xx+ to using CP DMA for the blit copy callback
drm/radeon: switch r6xx+ to using CP DMA for the blit copy callback

CP DMA is lighter weight than using the 3D engine.

Signed-off-by: Alex Deucher <08dc22c6156113f2deff178e35e3ed9b24d6af9e@amd.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs