When new node becomes enable by hot-add, new sysfs file must be created for
new node.  So, if new node is enabled by add_memory(), register_one_node() is
called to create it.  In addition, I386's arch_register_node() and a part of
register_nodes() of powerpc are consolidated to register_one_node() as a
generic_code().

This is tested by Tiger4(IPF) with node hot-plug emulation.

Signed-off-by: Keiichiro Tokunaga <tokuanga.keiich@jp.fujitsu.com>
Signed-off-by: Yasunori Goto <y-goto@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>