x86, mm: Fix node_possible_map logic

Recently there were some changes to the meaning of node_possible_map,
and it is quite strange:

- the node without memory would be set in node_possible_map
- but some node with less NODE_MIN_SIZE will be kicked out of node_possible_map.

fix it by adding strict_setup_node_bootmem().

Also, remove unparse_node().

so result will be:

1. cpu_to_node() will return online node only (nearest one)
2. apicid_to_node() still returns the node that could be not online but is set
   in node_possible_map.
3. node_possible_map will include nodes that mem on it are less NODE_MIN_SIZE

v2: after move_cpus_to_node change.

[ Impact: get node_possible_map right ]

Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Tested-by: Jack Steiner <steiner@sgi.com>
LKML-Reference: <4A0C49BE.6080800@kernel.org>
[ v3: various small cleanups and comment clarifications ]
Signed-off-by: Ingo Molnar <mingo@elte.hu>