net: phy: force phy suspend when calling phy_stop

Some ethernet drivers may call phy_start() and phy_stop() from
ndo_open() and ndo_close() respectively.

When network cable is unconnected, and operate like below:
step 1: ifconfig ethX up -> ndo_open -> phy_start ->start
autoneg, and phy is no link.
step 2: ifconfig ethX down -> ndo_close -> phy_stop -> just stop
phy state machine.

This patch forces phy suspend even phydev->link is off.

Signed-off-by: Jian Shen <shenjian15@huawei.com>
Reviewed-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>