blk-mq: Avoid that submitting a bio concurrently with device removal triggers a crash

Because blkcg_exit_queue() is now called from inside blk_cleanup_queue()
it is no longer safe to access cgroup information during or after the
blk_cleanup_queue() call. Hence protect the generic_make_request_checks()
call with blk_queue_enter() / blk_queue_exit().

Reported-by: Ming Lei <ming.lei@redhat.com>
Fixes: a063057d ("block: Fix a race between request queue removal and the block cgroup controller")
Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Joseph Qi <joseph.qi@linux.alibaba.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>