drm/amdgpu: revert "disable bulk moves for now"

This reverts commit a213c2c7.

The changes to fix this should have landed in 5.1.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Zhou, David(ChunMing) <David1.Zhou@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>