[PATCH] ppc64: add early_pfn_to_nid

Provide an implementation of early_pfn_to_nid for PPC64.  This is used by
memory models to determine the node from which to take allocations before the
memory allocators are fully initialised.

Signed-off-by: Andy Whitcroft <apw@shadowen.org>
Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
Signed-off-by: Martin Bligh <mbligh@aracnet.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>