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
hammerhead: Optimize I/O scheduling

noop is already default I/O scheduler.

Change-Id: I206600d91633bc140b4363b026669ba8074d6371