USB: MAINTAINERS: cxacru

Make cxacru an orphan. I still have a few of these devices for testing
but haven't had an ADSL1 connection for several years.

Signed-off-by: Simon Arlott <simon@fire.lp0.eu>
Cc: Duncan Sands <baldrick@free.fr>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>