sh: memory hot-add for sparsemem users support.

This enables simple hotplug support for sparsemem users. Presently
this only permits memory being added in to node 0 on ZONE_NORMAL.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>

diff --cc arch/sh/mm/Kconfig
Simple merge

diff --cc arch/sh/mm/init.c
Simple merge

diff --cc mm/Kconfig
Simple merge