[PATCH] typeof __page_to_pfn with SPARSEMEM=y

With CONFIG_SPARSEMEM=y:

mm/rmap.c:579: warning: format '%lx' expects type 'long unsigned int', but argument 2 has type 'int'

Make __page_to_pfn() return unsigned long.
Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/asm-generic/memory_model.h

@@ -54,7 +54,7 @@
 #define __page_to_pfn(pg)					\
 ({	struct page *__pg = (pg);				\
 	int __sec = page_to_section(__pg);			\
-	__pg - __section_mem_map_addr(__nr_to_section(__sec));	\
+	(unsigned long)(__pg - __section_mem_map_addr(__nr_to_section(__sec)));	\
 })
 
 #define __pfn_to_page(pfn)				\