staging: comedi: deprecate loading firmware with comedi_config

All the comedi drivers have been converted to use the request_firmware()
hotplug interface. The COMEDI_DEVCONFIG ioctl support for passing the
firmware blob as 'aux_data' is no longer required.

Remove the feature and give the user a dev_warn message if it is
attempted.

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>