[PATCH] powerpc: Minor numa memory code cleanup

I started to add missing of_node_put() calls to the routines that
determine the number of cells for memory.  Decided to combine the
routines instead of making separate node lookups.  Changed variable
names to help with some confusion as to meaning.

Signed-off-by: Mike Kravetz <kravetz@us.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>