net: tcp_probe: also include rcv_wnd next to snd_wnd

It is helpful to sometimes know the TCP window sizes of an established
socket e.g. to confirm that window scaling is working or to tweak the
window size to improve high-latency connections, etc etc. Currently the
TCP snooper only exports the send window size, but not the receive window
size. Therefore, also add the receive window size to the end of the
output line.

Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>