drm/amdgpu: support sdma struct v2 fw init

Support SDMA firmware init on common function for sdma v2 struct.

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>