kernel: work_q: Document implications of default sys work_q priority

Default value of CONFIG_SYSTEM_WORKQUEUE_PRIORITY is -1, which means
it's run by the cooperative thread. Explicitly mention (in the Kconfig
help) that it means that any work handler submited to this default
queue won't be preempted by some other thread (which is generally
good, but worth documenting explicitly).

Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>
1 file changed