blk-mq: Fix memory leak in blk_mq_init_allocated_queue error handling

If blk_mq_init_allocated_queue->elevator_init_mq fails, need to release
the previously requested resources.

Fixes: d3484991

 ("blk-mq-sched: allow setting of default IO scheduler")
Signed-off-by: zhengbin <zhengbin13@huawei.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>