net: shell: Print TX and RX threads stacks with more info

The "net stacks" command was printing TX or RX thread values so
that it was not possible to use the values in debugging easily.
Add traffic class value when printing the info so that it is
easy to see what TX or RX queue is doing.

Signed-off-by: Jukka Rissanen <jukka.rissanen@linux.intel.com>