net/handshake: Fix uninitialized local variable

trace_handshake_cmd_done_err() simply records the pointer in @req,
so initializing it to NULL is sufficient and safe.
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Fixes: 3b3009ea ("net/handshake: Create a NETLINK service for handling handshake requests")
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/handshake/netlink.c

@@ -157,8 +157,8 @@ int handshake_nl_accept_doit(struct sk_buff *skb, struct genl_info *info)
 int handshake_nl_done_doit(struct sk_buff *skb, struct genl_info *info)
 {
 	struct net *net = sock_net(skb->sk);
+	struct handshake_req *req = NULL;
 	struct socket *sock = NULL;
-	struct handshake_req *req;
 	int fd, status, err;
 
 	if (GENL_REQ_ATTR_CHECK(info, HANDSHAKE_A_DONE_SOCKFD))