ASoC: wm_adsp: Make compressed buffers optional

Newer firmwares will support compressed buffers that may or may not
exist, for example debugging streams. Update the driver to make a
compressed stream optional. A warning will still be generated at DSP
boot time and opening the stream will fail if the compressed buffer in
question does not exist, however the DSP can still be booted and other
features used.

Signed-off-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Link: https://lore.kernel.org/r/20220210172053.22782-2-ckeepax@opensource.cirrus.com
Signed-off-by: Mark Brown <broonie@kernel.org>