ASoC: nau8821: Improve AMIC recording performance.

Since the hardware may be designed as a single-ended input, the headset mic
record only supports single-ended input on the left side. This patch
will enhance microphone recording performance for single-end.

Signed-off-by: Seven Lee <wtli@nuvoton.com>
Link: https://lore.kernel.org/r/20230823071244.1861487-2-wtli@nuvoton.com


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