ASoC: rt5682: remove empty default case

Removes empty default case.  Also adds a missing break statement.

Signed-off-by: Tzung-Bi Shih <tzungbi@google.com>
Link: https://lore.kernel.org/r/20200430082231.151127-4-tzungbi@google.com


Signed-off-by: Mark Brown <broonie@kernel.org>