x86-64, NUMA: Make emulation code build numa_meminfo and share the registration path

NUMA emulation code built nodes[] array and had its own registration
path to set up the emulated nodes.  Update it such that it generates
emulated numa_meminfo and returns control to initmem_init() and shares
the same registration path with non-emulated cases.

Because {acpi|amd}_fake_nodes() expect nodes[] parameter,
fake_physnodes() now generates nodes[] from numa_meminfo.  This will
go away with further updates.

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>