vmscan: zone_reclaim don't call disable_swap_token()

Swap token don't works when zone reclaim is enabled since it was born.
Because __zone_reclaim() always call disable_swap_token() unconditionally.

This kill swap token feature completely.  As far as I know, nobody want to
that.  Remove it.

Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Acked-by: Rik van Riel <riel@redhat.com>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
Cc: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>