Add sdma firmware struct version 2 to support new SDMA v6 and forward
firmware version.

v2: squash in fix
Signed-off-by: Likun Gao <Likun.Gao@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>