staging: comedi: usbduxsigma: Declare MODULE_FIRMWARE usage

Cc: Ian Abbott <abbotti@mev.co.uk>
Cc: Mori Hess <fmhess@users.sourceforge.net>
Cc: Bernd Porr <berndporr@f2s.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>