Local variable `i' is a) misleadingly-named for an `enum zone_type' and b)
used for indexing zones as well as nodes as well as node_maps.

Make it an `int'.
Reported-by: NFrans Pop <elendil@planet.nl>
Cc: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>