ASoC: SOF: IPC: make sof_ipc_window monosized

ASoC: SOF: IPC: make sof_ipc_window monosized

This step is needed to add possibility to pack sof_ipc_window inside
another one in used FW build tools - for example in extended manifest.
Structure reusability leads to easy parsing function reuse, so source
code is shorter and easier to maintain.

Using structures with constant size is less tricky and properly
supported by each toolchain by contrast to variable size elements.

This is minor ABI change - backward compatibility is kept.

Signed-off-by: Karol Trzcinski <karolx.trzcinski@linux.intel.com>
Reviewed-by: Guennadi Liakhovetski <guennadi.liakhovetski@linux.intel.com>
Reviewed-by: Kai Vehmanen <kai.vehmanen@linux.intel.com>
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Link: https://lore.kernel.org/r/20200825235854.1588034-2-ranjani.sridharan@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>