USB: serial: ftd_sio: implement sysrq handling on break

Change driver to make use of the new functions in
include/linux/usb/serial.h so as to allow the driver to handle the
sysrq

Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>