Powerplay uses cgs to load the firmware so add a function
to release it as well to avoid leaking it on driver unload.
Signed-off-by: Monk Liu <Monk.Liu@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>