staging: comedi: me4000: Check for unsupported INSN_CONFIG.

The INSN_CONFIG handler for the DIO subdevice should error out for
unsupported configuration instruction codes.

Also fix incorrect use of constant COMEDI_OUTPUT where
INSN_CONFIG_DIO_OUTPUT was meant.

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