staging: comedi: dt2801: do INSN_CONFIG properly for DIO subdevice.

Handle INSN_CONFIG_DIO_INPUT, INSN_CONFIG_DIO_OUTPUT and
INSN_CONFIG_DIO_QUERY in data[0].

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