UPSTREAM: block/mq-deadline: Add an invariant check

Check a statistics invariant at module unload time. When running
blktests, the invariant is verified every time a request queue is
removed and hence is verified at least once per test.

Bug: 293845137
(cherry picked from commit 32f64cad)
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: Niklas Cassel <Niklas.Cassel@wdc.com>
Cc: Hannes Reinecke <hare@suse.de>
Change-Id: I9bff99de736f0b18a49be9512d9123bf50a82fac
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20210927220328.1410161-3-bvanassche@acm.org


Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Xiuhong Wang <xiuhong.wang@unisoc.com>