drm/amdgpu: add CAP fw loading

The CAP fw is for enabling driver compatibility. Currently, it only
enabled for vega10 VF.

Signed-off-by: Zhigang Luo <zhigang.luo@amd.com>
Reviewed-by: Shaoyun Liu <Shaoyun.Liu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>