atl1c: Disable L0S when no cable link

L0S might be unstable if no cable link, only enable it when link up.

Signed-off-by: xiong <xiong@qca.qualcomm.com>
Tested-by: Liu David <dwliu@qca.qualcomm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>