i386 mm: use pte_update() in ptep_test_and_clear_dirty()

It is not safe to use pte_update_defer() in ptep_test_and_clear_young():
its only user, /proc/<pid>/clear_refs, drops pte lock before flushing TLB.
Use the safe though less efficient pte_update() paravirtop in its place.
Likewise in ptep_test_and_clear_dirty(), though that has no current use.

These are macros (header file dependency stops them from becoming inline
functions), so be more liberal with the underscores and parentheses.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Cc: Zachary Amsden <zach@vmware.com>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>