staging: octeon: fix build failure with XFRM enabled

skb->sp doesn't exist anymore in the next-next tree, so mips defconfig
no longer builds.  Use helper instead to reset the secpath.

Not even compile tested.

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reported-by: Guenter Roeck <linux@roeck-us.net>
Fixes: 4165079b ("net: switch secpath to use skb extension infrastructure")
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/staging/octeon/ethernet-tx.c

@@ -359,8 +359,7 @@ int cvm_oct_xmit(struct sk_buff *skb, struct net_device *dev)
 	dst_release(skb_dst(skb));
 	skb_dst_set(skb, NULL);
 #ifdef CONFIG_XFRM
-	secpath_put(skb->sp);
-	skb->sp = NULL;
+	secpath_reset(skb);
 #endif
 	nf_reset(skb);