Add cpu scaling governor policy

Makes it possible to configure mce so that "interactive" scaling
governor is used when device is running in normal UI state and
"performance" when device is booting up or shutting down.

Configuration via /etc/mce/NN-adaptation-name.ini files that specify
Default and Interactive sections, for example:
  [CPUScalingGovernorDefault]
  path1=/sys/devices/system/cpu/cpu*/cpufreq/scaling_governor
  data1=performance
  path2=
  [CPUScalingGovernorInteractive]
  path1=/sys/devices/system/cpu/cpu*/cpufreq/scaling_governor
  data1=interactive
  path2=

The mcetool utility can be used to override the policy via:
  mcetool -S automatic|performance|interactive
This setting persists over mce restarts / device reboots.

[mce] Add cpu scaling governor policy
Decouple suspend policy and cpu scaling governor policy

The cpu scaling governor policy uses separate ENABLE_CPU_GOVERNOR build
time flag instead of piggybaggin to the ENABLE_WAKELOCKS used by suspend
policy.

The code that is used by both was refactored not to use suspend_ prefix.
Fix indentaton
Do not silently discard excess CPUScalingGovernor settings
Do not use performance cpu scaling governor in act dead mode

The intent is that the performance scaling governor is used only
in transitional states (bootup, shutdown, etc).
Reject bogus paths in CPUScalingGovernor settings

Writes based on configuration data are limited to subtree under
/sys/devices/system/cpu/.
Merge pull request #56 from spiiroin/cpu_scaling_governor

Add CPU scaling governor policy