net: stmmac: Do not stop PHY if WoL is enabled

If WoL is enabled we can't really stop the PHY, otherwise we will not
receive the WoL packet. Fix this by telling phylink that only the MAC is
down and only stop the PHY if WoL is not enabled.

Fixes: 74371272 ("net: stmmac: Convert to phylink and remove phylib logic")
Signed-off-by: Jose Abreu <Jose.Abreu@synopsys.com>
Signed-off-by: David S. Miller <davem@davemloft.net>