net: fec: fix NULL pointer dereference in fec_enet_timeout_work

This patch initialises the fep->netdev pointer. This pointer was not
initialised at all, but is used in fec_enet_timeout_work and in some
error paths.

Signed-off-by: Hubert Feurstein <h.feurstein@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>