staging/wlan-ng, prism2usb: replace completion_bh tasklet with work

staging/wlan-ng, prism2usb: replace completion_bh tasklet with work

Tasklets have long been deprecated as being too heavy on the system
by running in irq context - and this is not a performance critical
path. If a higher priority process wants to run, it must wait for
the tasklet to finish before doing so.

The completion_bh tasklet will now run in process context and have
further concurrency (tasklets being serialized among themselves),
but this is done holding the ctlxq.lock, so it should be fine.

Signed-off-by: Davidlohr Bueso <dave@stgolabs.net>
Link: https://lore.kernel.org/r/20220411151620.129178-4-dave@stgolabs.net
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>