The ALLOW_SR registers might not always be available.
Signed-off-by: NKen Chalmers <ken.chalmers@amd.com>
Reviewed-by: NTony Cheng <Tony.Cheng@amd.com>
Acked-by: NHarry Wentland <harry.wentland@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>