cpu_idle_job: relax a bit
cpu_idle_job: relax a bit

This *dramatically* improves kernel boot time with GCOV builds

from ~3minutes between loading kernel and switching the HILE
bit down to around 10 seconds.

Signed-off-by: Stewart Smith <ec31ab75ddf977353c8f660f92ea8b23f64aef25@linux.vnet.ibm.com>

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