x86: change maximum NR_CPUS to 4096 and MAX_NUMNODES to 512

  * Change the range of NR_CPUS from 2-255 to 2-4096 and change the
    range of MAX_NUMNODES (NODES_SHIFT) from 1-32768 to 1-512.

  * Alter comment about how much each increment of NR_CPUS consumes.
    (This was found by configuring for 256 cpus and then 512 cpus
     and dividing the difference by 256.)

Signed-off-by: Mike Travis <travis@sgi.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Dave Jones <davej@codemonkey.org.uk>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>