blk-cgroup: Kill the header printed at the start of blkio.weight_device file

o Kill extra "dev weight" header which is printed when somebody reads
  blkio.weight_device file. This really seems to be out of convention. No other
  blkio files are printing any header at the start of file. I think it is ok
  to just print values and how to interpret values should be part of
  documentation.
Signed-off-by: NVivek Goyal <vgoyal@redhat.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

block/blk-cgroup.c

@@ -811,8 +811,6 @@ static int blkiocg_weight_device_read(struct cgroup *cgrp, struct cftype *cft,
 	struct blkio_cgroup *blkcg;
 	struct blkio_policy_node *pn;
 
-	seq_printf(m, "dev\tweight\n");
-
 	blkcg = cgroup_to_blkio_cgroup(cgrp);
 	if (!list_empty(&blkcg->policy_list)) {
 		spin_lock_irq(&blkcg->lock);