this is to prevent fence forever waiting if FLR occured
during register accessing.

v2:
use define instead of hardcode for the timeout msec
Signed-off-by: NMonk Liu <Monk.Liu@amd.com>
Reviewed-by: NChristian König <christian.koenig@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>