staging: comedi_fops.c whitespace fixes

Changed whitespaces in comedi/*.c to tabs where necessary. All .c
files within comedi now have no obvious style problems as reported by
checkpatch.pl
Signed-off-by: Florian Schmaus <fschmaus@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>