drm/amdgpu: support S&R fw load for gfx v12

Support Save & Restore related fw load with backdoor RLC
autoload type on gfx v12.

Signed-off-by: Likun Gao <Likun.Gao@amd.com>
Reviewed-by: Kenneth Feng <kenneth.feng@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>