Fixes gcc '-Wunused-but-set-variable' warning:
net/tipc/msg.c: In function 'tipc_msg_append':
net/tipc/msg.c:215:24: warning:
 variable 'prev' set but not used [-Wunused-but-set-variable]
commit 
0a3e060f340d ("tipc: add test for Nagle algorithm effectiveness")
left behind this, remove it.
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
 int tipc_msg_append(struct tipc_msg *_hdr, struct msghdr *m, int dlen,
                    int mss, struct sk_buff_head *txq)
 {
-       struct sk_buff *skb, *prev;
+       struct sk_buff *skb;
        int accounted, total, curr;
        int mlen, cpy, rem = dlen;
        struct tipc_msg *hdr;
 
        while (rem) {
                if (!skb || skb->len >= mss) {
-                       prev = skb;
                        skb = tipc_buf_acquire(mss, GFP_KERNEL);
                        if (unlikely(!skb))
                                return -ENOMEM;