Staging: comedi: fix export symbol warnings in ni_daq_700.c

This is a patch to the ni_daq_700.c file that fixes several EXPORT_SYMBOL
warnings found by the checkpatch.pl tool

Signed-off-by: Robert Babilon <robert.babilon@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>