ASoC: SDCA: Add completion for FDL start and stop

ASoC: SDCA: Add completion for FDL start and stop

Add some completions and a helper function to allow other parts of the
system to wait for FDL to complete. The sdca_fdl_sync() function will
wait until it completes a full time out without a new FDL request
happening, this ensures that even parts requiring multiple rounds of FDL
should be fully downloaded before the driver boot continues.

Reviewed-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Signed-off-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.dev>
Link: https://patch.msgid.link/20251020155512.353774-17-ckeepax@opensource.cirrus.com
Signed-off-by: Mark Brown <broonie@kernel.org>