tty: moxa: fix bit test in moxa_start()

commit 58112dfbfe02d803566a2c6c8bd97b5fa3c62cdc upstream.

This is supposed to be doing a shift before the comparison instead of
just doing a bitwise AND directly.  The current code means the start()
just returns without doing anything.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>