cma: decrease cc.nr_migratepages after reclaiming pagelist

reclaim_clean_pages_from_list() reclaims clean pages before migration so
cc.nr_migratepages should be updated.  Currently, there is no problem but
it can be wrong if we try to use the value in future.

Change-Id: I8b3f1238645ba1b3adcc0fe3c41e10f7074b9a96
Signed-off-by: Minchan Kim <minchan@kernel.org>
Acked-by: Mel Gorman <mgorman@suse.de>
Cc: Michal Nazarewicz <mina86@mina86.com>
Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Git-commit: beb51eaa88238daba698ad837222ad277d440b6d
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
[lauraa@codeaurora.org: Change cc to be structure instead of pointer]
Signed-off-by: Laura Abbott <lauraa@codeaurora.org>

Signed-off-by: franciscofranco <franciscofranco.1990@gmail.com>