fast-reboot: add sreset timeout detection and handling
fast-reboot: add sreset timeout detection and handling

Have the initiator wait for all its sreset targets to call in, and
time out after 200ms if they did not. Fail and revert to IPL reboot.

Testing indicates that after successful sreset_all_others(), it
takes less than 102ms (in hundreds of fast reboots) for secondaries
to call in. 100 of that is due to an initial delay, but core
un-splitting was not measured.

Signed-off-by: Nicholas Piggin <24829078df5003d9dd1dd871ca2aeb0b1cf95ef4@gmail.com>
Signed-off-by: Stewart Smith <ec31ab75ddf977353c8f660f92ea8b23f64aef25@linux.vnet.ibm.com>

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