spidernet: skb used after netif_receive_skb

The stats update code in spider_net_pass_skb_up() is touching the skb
after it's been passed up to the stack. To avoid that, just update the
stats first.

Signed-off-by: Florin Malita <fmalita@gmail.com>
Signed-off-by: Linas Vepstas <linas@austin.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>