mm/memblock.c: use PFN_DOWN

Replace ((x) >> PAGE_SHIFT) with the pfn macro.

Signed-off-by: Fabian Frederick <fabf@skynet.be>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/memblock.c b/mm/memblock.c
index 1467364..0aa0d2b 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -1402,9 +1402,8 @@
 	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;
 }