net: phy: use network device in phy_print_status

phy_print_status() currently uses dev_name(&phydev->dev) which will
usually result in printing something along those lines for Device Tree
aware drivers:

libphy: f0b60000.etherne:0a - Link is Down
libphy: f0ba0000.etherne:00 - Link is Up - 1000/Full

This is not terribly useful for network administrators or users since we
expect a network interface name to be able to correlate link events with
interfaces. Update phy_print_status() to use netdev_info() with
phydev->attached_dev which is the backing network device for our PHY
device. The leading dash is removed since netdev_info() prefixes the
messages with "<interface>: " already.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>