staging: comedi: fix coding style issues in comedi_fops.c

This is a patch to fix coding style
warnings found by checkpatch.pl tool

Signed-off-by: Raghavendra Chandra Ganiga <ravi23ganiga@gmail.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>