ASoC: SOF: add definitions for different IPC types

Add enum type to allow for different types of IPCs. The IPCv4 is
intended for Intel only as a convergence path with firmware used in
Windows. Follow-up patches will introduce different abstractions with
.ops and different search paths for firmware and topology files.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Reviewed-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Reviewed-by: Rander Wang <rander.wang@intel.com>
Reviewed-by: Péter Ujfalusi <peter.ujfalusi@linux.intel.com>
Link: https://lore.kernel.org/r/20220414184817.362215-2-pierre-louis.bossart@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>