Make the SOF control, PCM and PM code IPC agnostic

Merge series from Ranjani Sridharan <ranjani.sridharan@linux.intel.com>:

This series is a continuation to the SOF IPC abstraction work to support
the new IPC version introduced in the SOF firmware. It makes the top-level
control IO, PCM and PM code IPC-agnostic. Other than the first patch,
the rest are purely for abstraction and include no changes in
functionality.