staging: comedi: usbduxsigma: request firmware synchronously

Change the request_firmware_nowait() to a request_firmware() so
that the usb_driver (*probe) can continue with the comedi_driver
(*auto_attach).

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>