ksz884x: remove unnecessary setting of skb->dev

skb->dev is being unnecessarily set during ring init.  It is already being set
to the proper value when eth_type_trans is called on packet receive, and the
skb->dev is not referenced anywhere else in the code.

Signed-off-by: Jon Mason <jdmason@kudzu.us>
Signed-off-by: David S. Miller <davem@davemloft.net>