[ALSA] hda-codec - Add missing Mic Boost for AD1986A codec

Added the missing 'Mic Boost' switch for AD1986A codec.
This influences largely on the recording level of mic-input on some boards.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@suse.cz>