stop_machine: Add caller debug info to queue_stop_cpus_work

Most callsites were covered by commit

  a8b62fd0 ("stop_machine: Add function and caller debug info")

but this skipped queue_stop_cpus_work(). Add caller debug info to it.

Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20201210163830.21514-2-valentin.schneider@arm.com