net: phy: utilize phy_suspend and phy_resume

phy_suspend and phy_resume are an abstraction on top of the PHY device
driver suspend and resume callbacks, utilize those since they are the
proper interface to suspending and resuming a PHY device.

Acked-by: Fugang Duan <B38611@freescale.com>
Tested-by: Fugang Duan <B38611@freescale.com>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>