drm/amdkfd: sienna_cichlid virtual function support

amdkfd add support for sienna_cichlid virtual function

Signed-off-by: shaoyunl <shaoyun.liu@amd.com>
Reviewed-by: Yong Zhao <Yong.Zhao@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>