blk-iocost: fix lockdep warning on blkcg->lock

blk-iocost: fix lockdep warning on blkcg->lock

blkcg->lock depends on q->queue_lock which may depend on another driver
lock required in irq context, one example is dm-thin:

	Chain exists of:
	  &pool->lock#3 --> &q->queue_lock --> &blkcg->lock

	 Possible interrupt unsafe locking scenario:

	       CPU0                    CPU1
	       ----                    ----
	  lock(&blkcg->lock);
	                               local_irq_disable();
	                               lock(&pool->lock#3);
	                               lock(&q->queue_lock);
	  <Interrupt>
	    lock(&pool->lock#3);

Fix the issue by using spin_lock_irq(&blkcg->lock) in ioc_weight_write().

Cc: Tejun Heo <tj@kernel.org>
Reported-by: Bruno Goncalves <bgoncalv@redhat.com>
Link: https://lore.kernel.org/linux-block/CA+QYu4rzz6079ighEanS3Qq_Dmnczcf45ZoJoHKVLVATTo1e4Q@mail.gmail.com/T/#u
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20210803070608.1766400-1-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>