staging: comedi: ni_mio_cs: convert to auto attach

Convert this pcmcia driver to the comedi auto attach mechanism.

This allows getting rid of the "hack" needed to pass the pcmcia_device
pointer from the pcmcia_driver to the comedi_driver.

We still need the boardinfo because ni_mio_common.c uses it. Cleanup
ni_getboardtype() so it returns a pointer to the boardinto instead
of the index.

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>