Introduce IPC abstraction for SOF topology parsing

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

This patchset makes the topology parsing layer in the SOF driver
IPC-agnostic in preparation for supporting the new IPC version
introduced in the SOF firmware. These patches purely contain abstraction
changes for the current IPC version (IPC3) supported and do not introduce
any functional changes.