powerpc/mm: Fixup _HPAGE_CHG_MASK

This was wrongly updated by commit 7aa9a23c69ea ("powerpc, thp: remove
infrastructure for handling splitting PMDs") during the last merge
window. Fix it up.

This could lead to incorrect behaviour in THP and/or mprotect(), at a
minimum.

Fixes: 7aa9a23c69ea ("powerpc, thp: remove infrastructure for handling splitting PMDs")
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/include/asm/book3s/64/hash.h

@@ -50,7 +50,9 @@
  * set of bits not changed in pmd_modify.
  */
 #define _HPAGE_CHG_MASK (PTE_RPN_MASK | _PAGE_HPTEFLAGS | _PAGE_DIRTY | \
-			 _PAGE_ACCESSED | _PAGE_THP_HUGE)
+			 _PAGE_ACCESSED | _PAGE_THP_HUGE | _PAGE_PTE | \
+			 _PAGE_SOFT_DIRTY)
+
 
 #ifdef CONFIG_PPC_64K_PAGES
 #include <asm/book3s/64/hash-64k.h>