staging: comedi: usbduxsigma: remove check of 'probed' in (*cancel) functions

The comedi_device private data variable 'probed' is set after the usb_driver
has completed its (*probe) before calling comedi_usb_auto_config(). That
function calls the comedi_driver (*auto_attach) which will set the
comedi_device 'private' variable and initialize the subdevices.

The subdevice (*cancel) functions can only be called after the (*auto_attach)
has completed successfully so the sanity checks of 'probed' are unnecessary.
Remove them.

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>