net: tcp2: Ack any data received in FIN_WAIT_1 state

If we receive any data in FIN_WAIT_1, then ack it even if we
are discarding it.

Fixes #33986

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