Describe NUMA node sysfs files/attributes.

Note that for the specific dates and contacts I couldn't find,
I left it as default for Oct 2002 and linux-mm.
Signed-off-by: NDavidlohr Bueso <davidlohr.bueso@hp.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>