net: ipv6: fix wrong ping_v6_sendmsg return value

[net-next commit fbfe80c890]

ping_v6_sendmsg currently returns 0 on success. It should return
the number of bytes written instead.

Bug: 12800827
Change-Id: I7ed17dc61afbb68a84908e67e44db976ec812bad
Signed-off-by: Lorenzo Colitti <lorenzo@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/ping.c

@@ -212,5 +212,8 @@ int ping_v6_sendmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
 						 len);
 	}
 
-	return err;
+	if (err)
+		return err;
+
+	return len;
 }