drm/amdgpu: use SDMA round robin for VM updates v3

Distribute the load on both rings.

v2: use a loop for the initialization
v3: agd: rebase on upstream

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
6 files changed