x86, NUMA: trivial cleanups

* Kill no longer used struct bootnode.

* Kill dangling declaration of pxm_to_nid() in numa_32.h.

* Make setup_node_bootmem() static.

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>