Add MHS, tool for simple media handling status reporting

Adds a small tool for reporting the status of, until now, the state of the MFC
hardware decoder and the camera, for use in other drivers.

To be expanded in the future with a proper notifier block architecture for
clean registration and callbacks to subscribing members.
mdnie-control: Use MHS for video scenarios
mhs: Temporary forced updates of audio mic level and mdnie

To be removed when I write a proper notifier architecture for the driver.