tools: kwboot: Disable tty interbyte timeout

Function kwboot_tty_recv() has its own handling of read timeout, we
don't need to do set it in tty settings.

Signed-off-by: Pali Rohár <pali@kernel.org>
Signed-off-by: Marek Behún <marek.behun@nic.cz>
Reviewed-by: Stefan Roese <sr@denx.de>