staging: comedi: restrict comedi_auto_config() to single driver

comedi_auto_config() only needs to consider a single struct
comedi_driver object, but it currently calls comedi_device_attach()
which looks at all struct comedi_driver objects registered with the
Comedi core.

Instead, call the recently added comedi_auto_config_helper() with a new
wrapper comedi_auto_config_wrapper() to mimic the effect of
comedi_device_attach() for a single struct comedi_driver.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>