staging: comedi: dt9812: use module_comedi_usb_driver()

Now that the semaphore used by the comedi_driver is initialized
when the comedi_device private data is allocated, the module_init()
in this driver just clears the 'slot' data before calling
comedi_usb_driver_register(). This static data will already be
cleared when the driver is loaded.

Replace the module_{init,exit}() with the module_comedi_usb_driver()
macro to remove the boilerplate code.

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>