staging: comedi: addi_apci_3xxx: remove COMEDI_SUBD_TTLIO

This driver abuses the enum comedi_subdevice_type by redefining
enum 11 - COMEDI_SUBD_SERIAL as COMEDI_SUBD_TTLIO. The subdevice
that uses COMEDI_SUBD_TTLIO is a TTL Digital Input/Output subdevice.

Remove COMEDI_SUBD_TTLIO and just use COMEDI_SUBD_DIO as the
subdevice type.

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>