staging: comedi: usbduxsigma: remove dev_{level} messages in submit urbs functions

The usbduxsub_submit_{In,Out}URBs() functions have a couple development
debug messages that are just added noise. Remove them.

Also, the sanity check of 'usbduxsub', the comedi_device private data, is
not necessary. The callers have already validated it. Remove the checks.

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>