kaiser: merged update

Merged fixes and cleanups, rebased to 4.9.51 tree (no 5-level paging).

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>