canbus: isotp: use new k_work API

[martinjaeger]

Replace soon-to-be-deprecated call to start queue.

Delayed work is not used here.

Remark:
While implementing the work queue changes, I realized that the local work queue is actually not used in the ISO-TP implementation. Instead, the work is always submitted to the system work queue with k_work_submit. A trivial fix did not work, so I opened issue #34862 to leave it for a separate PR.

[pabigot]

OK, but if it's not used maybe it should be removed.

[martinjaeger]

OK, but if it's not used maybe it should be removed.

True, but there are also Kconfig symbols associated to it, which could preliminarily break existing firmware if they are removed.

I was wondering if we can't use the system work queue permanently. @pabigot Is there any rule/recommendation when to use a dedicated work queue instead of the system work queue? Looking through other drivers both approaches seem to be common.

The BK issues are unrelated to this PR, btw.

[pabigot]

@pabigot Is there any rule/recommendation when to use a dedicated work queue instead of the system work queue? Looking through other drivers both approaches seem to be common.

https://docs.zephyrproject.org/latest/reference/kernel/threads/workqueue.html#system-workqueue

Ideally if the work handler can sleep don't use the system work queue, but some existing uses run afoul of that expectation which is why USB and maybe other subsystems got their own (sometimes optionally).

[alexanderwachter]

Danke @martinjaeger !

[galak]

Going to merge this and we can follow up cleanup / changes in a new PR.