mm: enable CONFIG_COMPACTION by default

mm: enable CONFIG_COMPACTION by default

Now that lumpy reclaim has been removed, compaction is the only way left
to free up contiguous memory areas.  It is time to just enable
CONFIG_COMPACTION by default.

Signed-off-by: Rik van Riel <[email protected]>
Cc: Mel Gorman <[email protected]>
Acked-by: Rafael Aquini <[email protected]>
Acked-by: Johannes Weiner <[email protected]>
Acked-by: Minchan Kim <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>