net: phy: smsc: fix link up detection in forced irq mode

Currently link up can't be detected in forced mode if polling
isn't used. Only link up interrupt source we have is aneg
complete which isn't applicable in forced mode. Therefore we
have to use energy-on as link up indicator.

Fixes: 73654945 ("net: phy: smsc: skip ENERGYON interrupt if disabled")
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>