cfq-iosched: free cic_index if blkio_alloc_blkg_stats fails

If we fail allocating the blkpg stats, we free cfqd and cfgq.
But we need to free the IDA cfqd->cic_index as well.

Signed-off-by: majianpeng <majianpeng@gmail.com>
Cc: stable@kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>