powerpc/mm: Fix _PAGE_CHG_MASK to protect _PAGE_SPECIAL

Fix _PAGE_CHG_MASK so that pte_modify() does not affect the _PAGE_SPECIAL bit.

Signed-off-by: Philippe Gerum <rpm@xenomai.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
3 files changed