Staging: comedi: fix checkpatch.pl warning in interrupt.h

No more need for a kernel version check now that we are in the main
kernel tree.

Cc: David Schleef <ds@schleef.org>
Cc: Frank Mori Hess <fmhess@users.sourceforge.net>
Cc: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>