ASoC: dt-bindings: nau8821: Add single-ended input feature

Add input with single-ended control.

Signed-off-by: Seven Lee <wtli@nuvoton.com>
Link: https://lore.kernel.org/r/20230823071244.1861487-1-wtli@nuvoton.com


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