[TCP]: tcp probe wraparound handling and other changes

Switch from formatting messages in probe routine and copying with
kfifo, to using a small circular queue of information and formatting
on read.  This avoids wraparound issues with kfifo, and saves one
copy.

Also make sure to state correct license, rather than copying off some
other driver I started with.

Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>