Summary:
For every other sensor the human readable name of cpu0 is "CPU 1" and so
on, except clock speed

Before (in ksysguardd -i)
ksysguardd> cpu/cpu0/sys?
CPU 1 System Load       0       100     %

ksysguardd> cpu/cpu0/clock?
CPU0 Clock Frequency    0       0       MHz

With this patch they're uniform

Doesn't make a big difference as SensorManager goes through a big
translation and disregards this anyway.

Test Plan: #plasma

Reviewers: ahiemstra

Reviewed By: ahiemstra

Subscribers: ahiemstra, plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D26857