ASoC: SDCA: Add missing default in switch in entity_pde_event()

ASoC: SDCA: Add missing default in switch in entity_pde_event()

The current code should be safe as the PDE widget only registers for the
two events handled in the switch statement. However, it is causing a
smatch warning and also is a little fragile to future code changes, add
a default case to avoid the warning and make the code more robust.

Fixes: 2c8b3a8e6aa8 ("ASoC: SDCA: Create DAPM widgets and routes from DisCo")
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
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/20250624122844.2761627-3-ckeepax@opensource.cirrus.com
Signed-off-by: Mark Brown <broonie@kernel.org>