hammerhead: Make SYSTEM owner of cpu online files

This is required for the Settings app to online cpus
before writing to cpufreq files.

Change-Id: I63530bfcf095a0fbc432a908272bc89bb1ad89eb
Merge branch 'cm-11.0' of https://github.com/CyanogenMod/android_device_lge_hammerhead into cd-4.4