powerpc/mm: Add option for non-atomic PTE updates to ppc64

ppc32 has it already, add it to ppc64 as a preliminary for adding
support for Book3E 64-bit support

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
diff --git a/arch/powerpc/include/asm/pte-hash64.h b/arch/powerpc/include/asm/pte-hash64.h
index b61b7e4..0419eeb 100644
--- a/arch/powerpc/include/asm/pte-hash64.h
+++ b/arch/powerpc/include/asm/pte-hash64.h
@@ -41,6 +41,8 @@
 #define _PTEIDX_SECONDARY	0x8
 #define _PTEIDX_GROUP_IX	0x7
 
+/* Hash table based platforms need atomic updates of the linux PTE */
+#define PTE_ATOMIC_UPDATES	1
 
 #ifdef CONFIG_PPC_64K_PAGES
 #include <asm/pte-hash64-64k.h>