TTY: crisv10, initialize tty_port

The tty_port used in the driver is left uninitialized. Add the
initialization there.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: Mikael Starvik <starvik@axis.com>
Acked-by: Jesper Nilsson <jesper.nilsson@axis.com>
Cc: linux-cris-kernel@axis.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>