[SK_BUFF]: Use skb_reset_network_header where the return of __pskb_pull was being used

It returns skb->data, so we can just use skb_reset_network_header after it.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>