Add HDMI-CEC service

This CL adds a system service handling HDMI-CEC protocol. The service
is equipped with the capability sending/receiving HDMI-CEC messages

Not all the messages are in place. Currently it has messages to support
a few features only, as follows:

- One touch play
- System information
- Routing control (partially - active source status maintenance only)
- Device OSD transfer
- Power status

It will be extended to cover the wider usages in the follow up CLs.

The CEC standard version referenced in the implementation is 1.3a.

Change-Id: Ifed0b02f52ebf098eddb3bd0987efbf353b7e8fe