staging: comedi: adv_pci_dio: absorb pci_dio_add_di()

This function initializes a digitial input subdevices. For aesthetics,
absorb it into the (*auto_attach).

Remove the improper initialization of the SDF_LSAMPL subdev_flag and
len_chanlist. These are only used by subdevices that support async
commands.

Also, remove the unnecessary 'specflags' from the diosubd_data. Only
the boardid subdevice uses it.

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>