staging: comedi: usbduxsigma: updated contact details and status

I've updated my contact details of the driver. I've also tested it
thoroughly and it works perfectly. I've changed the status to stable.

Signed-off-by: Bernd Porr <mail@berndporr.me.uk>
Reviewed-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>