[PATCH] AT91RM9200 Ethernet: Use dev_alloc_skb()

Use dev_alloc_skb() instead of alloc_skb().

It is also not necessary to adjust skb->len manually since that's
already done by skb_put().

Signed-off-by: Andrew Victor <andrew@sanpeople.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>