Our hook creates the sysctl node before root is mounted, but after cpu
is probed. It seems that k8temp can be loaded before the cpu module and,
in those cases, dev.cpu.0.temperature was not created.
PR: 124939
Instead use the worldwide known MAX() function.
This should fix problems with negative values showing up on
dev.cpu.%d.temperature.
This is slightly different from the fix in the PR.
Submitted by: KOIE Hidetaka <hide at koie.org>
PR: 123542
