staging: comedi: ni_daq_700: rename functions for DIO subdevice

Rename `subdev_700_insn()` to `daq700_dio_insn_bits()` and
`subdev_700_insn_config()` to `daq700_dio_insn_config()`.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>