ASoC: SOF: add INTEL_IPC4 plumbing

Merge series from Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>:

The INTEL_IPC4 protocol and firmware architecture will rely on
different sets of firmware binary and topology files. Some platforms
will only support INTEL_IPC4, some will support both INTEL_IPC4 and
SOF_IPC for development, and some will stay with the existing SOF_IPC.

This patchset adds new IPC definitions, and search paths for firmware
and topology files, along with means to override the default IPC type
and search paths for development. The firmware binary names are
aligned with those used by the Intel AVS driver to avoid duplicate
firmware installs, but the topology will have to differ due to driver
architecture differences.