[IPV6]: ip6_xmit: remove unnecessary NULL ptr check

The sk argument to ip6_xmit is never NULL nowadays since the skb->priority
assigment expects a valid socket.

Coverity #354

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/ip6_output.c

@@ -161,7 +161,7 @@ int ip6_output(struct sk_buff *skb)
 int ip6_xmit(struct sock *sk, struct sk_buff *skb, struct flowi *fl,
 	     struct ipv6_txoptions *opt, int ipfragok)
 {
-	struct ipv6_pinfo *np = sk ? inet6_sk(sk) : NULL;
+	struct ipv6_pinfo *np = inet6_sk(sk);
 	struct in6_addr *first_hop = &fl->fl6_dst;
 	struct dst_entry *dst = skb->dst;
 	struct ipv6hdr *hdr;