mm/memblock.c: use PFN_DOWN

Replace ((x) >> PAGE_SHIFT) with the pfn macro.
Signed-off-by: NFabian Frederick <fabf@skynet.be>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm/memblock.c

@@ -1402,9 +1402,8 @@ int __init_memblock memblock_search_pfn_nid(unsigned long pfn,
 	if (mid == -1)
 		return -1;
 
-	*start_pfn = type->regions[mid].base >> PAGE_SHIFT;
-	*end_pfn = (type->regions[mid].base + type->regions[mid].size)
-			>> PAGE_SHIFT;
+	*start_pfn = PFN_DOWN(type->regions[mid].base);
+	*end_pfn = PFN_DOWN(type->regions[mid].base + type->regions[mid].size);
 
 	return type->regions[mid].nid;
 }