staging: comedi: ni_tiocmd: make ni_tio_cmdtest() a proper comedi (*do_cmdtest)

Change the parameters to ni_tio_cmdtest() to make it a proper comedi
(*do_cmdtest) function. This allows using it directly and removing the
wrapper functions in the ni_660x and ni_mio_common modules.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>