fec: Fix PHC device log

Currently when booting a mx6 device we get the following on boot:

registered PHC device on eth%d

Fix it by printing the network device name only after it gets registered, so
that the following can be read now:

fec 2188000.ethernet eth0: registered PHC device 0

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: David S. Miller <davem@davemloft.net>