[TCP]: fix memory leak in net/ipv4/tcp_probe.c::tcpprobe_read()

Based upon a patch by Jesper Juhl.

Signed-off-by: James Morris <jmorris@namei.org>
Acked-by: Stephen Hemminger <shemminger@osdl.org>
Acked-by: Jesper Juhl <jesper.juhl@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>