mm: add node states sysfs class attributeS

Add a per node state sysfs class attribute file to /sys/devices/system/node
to display node state masks.

E.g., on a 4-cell HP ia64 NUMA platform, we have 5 nodes: 4 representing
the actual hardware cells and one memory-only pseudo-node representing a
small amount [512MB] of "hardware interleaved" memory.  With this patch, in
/sys/devices/system/node we see:

#ls -1F /sys/devices/system/node
has_cpu
has_normal_memory
node0/
node1/
node2/
node3/
node4/
online
possible
#cat /sys/devices/system/node/possible
0-255
#cat /sys/devices/system/node/online
0-4
#cat /sys/devices/system/node/has_normal_memory
0-4
#cat /sys/devices/system/node/has_cpu
0-3

Signed-off-by: Lee Schermerhorn <lee.schermerhorn@hp.com>
Acked-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>