blkcg: don't use percpu for merged stats

With recent plug merge updates, merged stats are no longer called for
plug merges and now only updated while holding queue_lock.  As
stats_lock is scheduled to be removed, there's no reason to use percpu
for merged stats.  Don't use percpu for merged stats.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index 1de32fe..6c8e3e3 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -29,10 +29,12 @@
 #ifdef CONFIG_BLK_CGROUP
 
 enum stat_type {
+	/* Number of IOs merged */
+	BLKIO_STAT_MERGED,
 	/* Total time spent (in ns) between request dispatch to the driver and
 	 * request completion for IOs doen by this cgroup. This may not be
 	 * accurate when NCQ is turned on. */
-	BLKIO_STAT_SERVICE_TIME = 0,
+	BLKIO_STAT_SERVICE_TIME,
 	/* Total time spent waiting in scheduler queue in ns */
 	BLKIO_STAT_WAIT_TIME,
 	/* Number of IOs queued up */
@@ -57,8 +59,6 @@
 	BLKIO_STAT_CPU_SERVICE_BYTES,
 	/* Total IOs serviced, post merge */
 	BLKIO_STAT_CPU_SERVICED,
-	/* Number of IOs merged */
-	BLKIO_STAT_CPU_MERGED,
 	BLKIO_STAT_CPU_NR
 };