Add a bare description of what /sys/devices/system/node/nodeX is.  Others
will follow in time but right now, none of that tree is documented.  The
existence of this file might at least encourage people to document new
entries.
Signed-off-by: NMel Gorman <mel@csn.ul.ie>
Reviewed-by: NKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>