mm: actually clear pmd_numa before invalidating

Commit 67f87463

 ("mm: clear pmd_numa before invalidating") cleared
the NUMA bit in a copy of the PMD entry, but then wrote back the
original

Signed-off-by: Matthew Wilcox <matthew.r.wilcox@intel.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>