staging: comedi: usbduxsigma: move usbduxsigma_firmware_upload()

For aesthetics, move this function near its caller. Also, move the
FIRMWARE_MAX_LEN define so its with the other firmware constants
and fix the whitespace.

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>