x86-64, NUMA: Kill mem_nodes_parsed

With all memory configuration information now carried in numa_meminfo,
there's no need to keep mem_nodes_parsed separate.  Drop it and use
numa_nodes_parsed for CPU / memory-less nodes.

A new helper numa_nodemask_from_meminfo() is added to calculate
memnode mask on the fly which is currently used to set
node_possible_map.

This simplifies NUMA init methods a bit and removes a source of
possible inconsistencies.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Cyrill Gorcunov <gorcunov@gmail.com>
Cc: Shaohui Zheng <shaohui.zheng@intel.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: H. Peter Anvin <hpa@linux.intel.com>

arch/x86/include/asm/numa_64.h

@@ -25,7 +25,6 @@ extern void setup_node_bootmem(int nodeid, unsigned long start,
 #define NODE_MIN_SIZE (4*1024*1024)
 
 extern nodemask_t numa_nodes_parsed __initdata;
-extern nodemask_t mem_nodes_parsed __initdata;
 
 extern int __cpuinit numa_cpu_node(int cpu);
 extern int __init numa_add_memblk(int nodeid, u64 start, u64 end);