x86, NUMA: Enable build of generic NUMA init code on 32bit

Generic NUMA init code was moved to numa.c from numa_64.c but is still
guaraded by CONFIG_X86_64.  This patch removes the compile guard and
enables compiling on 32bit.

* numa_add_memblk() and numa_set_distance() clash with the shim
  implementation in numa_32.c and are left out.

* memory_add_physaddr_to_nid() clashes with 32bit implementation and
  is left out.

* MAX_DMA_PFN definition in dma.h moved out of !CONFIG_X86_32.

* node_data definition in numa_32.c removed in favor of the one in
  numa.c.

There are places where ulong is assumed to be 64bit.  The next patch
will fix them up.  Note that although the code is compiled it isn't
used yet and this patch doesn't cause any functional change.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>