[ALPS08748521] ASoC: mt6681 LDO always on

[Description]
Keep AUD LDO always on to prevent micbias voltage unstable

[Test]
accdet intsert test: PASS

MTK-Commit-Id: 92334d034ca98f0a8b70fe272fd14a7b458ee50c

CR-Id: ALPS08748521
Feature: alsa_codec
Signed-off-by: Ting-Fang Hou <ting-fang.hou@mediatek.com>
Change-Id: I1c7b991d70d927bba1f4340288978803f85bb18c