Here is an updated version of the patch that panics if no memory is
found as Nathan suggested.  I'm still concerned that panic strings
(not just the one added here) at this stage of booting do not show
up on my system.  But, that is an issue separate from this patch.

Combine get_mem_*_cells() routines to avoid multiple memory node
lookups.  Added missing of_node_put() call.  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>