Factor out memblk handling from srat_64.c into two functions in
numa_64.c.  This patch doesn't introduce any behavior change.  The
next patch will make all init methods use these functions.

- v2: Fixed build failure on 32bit due to misplaced NR_NODE_MEMBLKS.
      Reported by Ingo.
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>