mm, vmscan: remove redundant check in shrink_zones()

As pointed out by Minchan Kim, shrink_zones() checks for populated zones
in a zonelist but a zonelist can never contain unpopulated zones.  While
it's not related to the node-lru series, it can be cleaned up now.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Mel Gorman <[email protected]>
Suggested-by: Minchan Kim <[email protected]>
Acked-by: Minchan Kim <[email protected]>
Acked-by: Johannes Weiner <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Author: gormanm

mm/vmscan.c

@@ -2605,9 +2605,6 @@ static void shrink_zones(struct zonelist *zonelist, struct scan_control *sc)
 
 	for_each_zone_zonelist_nodemask(zone, z, zonelist,
 					sc->reclaim_idx, sc->nodemask) {
-		if (!populated_zone(zone))
-			continue;
-
 		/*
 		 * Take care memory controller reclaiming has small influence
 		 * to global LRU.