unify pfn_to_page take 2 [17/25] ppc funcs

Index: test-layout-free-zone/include/asm-ppc/page.h
===================================================================
@@ -148,9 +148,7 @@ extern int page_is_ram(unsigned long pfn
 
 #define __pa(x) ___pa((unsigned long)(x))
 #define __va(x) ((void *)(___va((unsigned long)(x))))
-
-#define pfn_to_page(pfn)	(mem_map + ((pfn) - PPC_PGSTART))
-#define page_to_pfn(page)	((unsigned long)((page) - mem_map) + PPC_PGSTART)
+#define ARCH_PFN_OFFSET		PPC_PGSTART
 #define virt_to_page(kaddr)	pfn_to_page(__pa(kaddr) >> PAGE_SHIFT)
 #define page_to_virt(page)	__va(page_to_pfn(page) << PAGE_SHIFT)