ASoC: rt5682: change SAR voltage threshold

To fix errors in some 4 poles headset detection cases,
this patch adjusts the voltage threshold for mic detection.

Signed-off-by: Shuming Fan <shumingf@realtek.com>
Link: https://lore.kernel.org/r/20201126092759.9427-1-shumingf@realtek.com


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