USb: Break support for WinChipHead CH341 340 USB->Serial "chip"

Here is a patch to the ch341 driver which adds serial break support.

Signed-off-by: Tim Small <tim@seoss.co.uk>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>