sc92031: use netdev_alloc_skb

Use netdev_alloc_skb since it handles any NUMA node memory localtion issues
and sets skb->dev. Since device driver was not setting skb->dev, I bet
filter rules based on device would not work.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>