ASoC: rt722-sdca-sdw: add silence detection register as volatile

[ Upstream commit 968c974c

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Including silence detection register as volatile.

Signed-off-by: Jack Yu <jack.yu@realtek.com>
Link: https://msgid.link/r/c66a6bd6d220426793096b42baf85437@realtek.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>