net: fec: Fix build due to wrong dev annotation

commit 21a4e469

 (netdev: ethernet dev_alloc_skb to netdev_alloc_skb)
should have used "ndev" instead of "dev".

This causes the following build errors:

drivers/net/ethernet/freescale/fec.c: In function 'fec_enet_rx':
drivers/net/ethernet/freescale/fec.c:714: error: 'dev' undeclared (first use in this function)
drivers/net/ethernet/freescale/fec.c:714: error: (Each undeclared identifier is reported only once
drivers/net/ethernet/freescale/fec.c:714: error: for each function it appears in.)
drivers/net/ethernet/freescale/fec.c: In function 'fec_enet_alloc_buffers':
drivers/net/ethernet/freescale/fec.c:1213: error: 'dev' undeclared (first use in this function)

Fix it, so that fec driver can be built again.

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