cpu: Better output when waiting for a very long job
cpu: Better output when waiting for a very long job

Instead of printing at the end if the job took more than 1s,
print in the loop every 30s along with a backtrace. This will
give us some output if the job is deadlocked.

Signed-off-by: Benjamin Herrenschmidt <a7089bb6e7e92505d88aaff006cbdd60cc9120b6@kernel.crashing.org>
[stewart: bump to 30s rather than 5s, preserve PR_DEBUG for >1s]
Signed-off-by: Stewart Smith <ec31ab75ddf977353c8f660f92ea8b23f64aef25@linux.ibm.com>

open-power/skiboot,shenki/skiboot,open-power/skiboot,open-power/skiboot,open-power/skiboot,legoater/skiboot,shenki/skiboot,stewart-ibm/skiboot,legoater/skiboot,legoater/skiboot,shenki/skiboot,legoater/skiboot,open-power/skiboot,qemu/skiboot,legoater/skiboot,qemu/skiboot,qemu/skiboot,shenki/skiboot,qemu/skiboot,stewart-ibm/skiboot,qemu/skiboot,stewart-ibm/skiboot,shenki/skiboot