block: avoid deferral of blk_release_queue() work

Commit dc9edc44de6c ("block: Fix a blk_exit_rl() regression") moved
the blk_release_queue() into a workqueue after a splat floated around
with some work here which could sleep in blk_exit_rl().

On recent commit db6d9952356 ("block: remove request_list code") though
Jens Axboe removed this code, now merged since v5.0. We no longer have
to defer this work.

By doing this we also avoid failing to detach / attach a block
device with a BLKTRACESETUP. This issue can be reproduced with
break-blktrace [0] using:

  break-blktrace -c 10 -d -s

The kernel does not crash without this commit, it just fails to
create the block device because the prior block device removal
deferred work is pending. After this commit we can use the above
flaky use of blktrace without an issue.

[0] https://github.com/mcgrof/break-blktrace

Cc: Bart Van Assche <bvanassche@acm.org>
Cc: Omar Sandoval <osandov@fb.com>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Nicolai Stange <nstange@suse.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Michal Hocko <mhocko@kernel.org>
Suggested-by: Nicolai Stange <nstange@suse.de>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>