max98090 spec states that chip needs to be in turned-on state to supply
mic bias. Enable SHDN dapm widget along with MICBIAS widget to
actually turn on mic bias for proper headset button detection.
This is similar to cht_ti_jack_event in
sound/soc/intel/boards/cht_bsw_max98090_ti.c.

Note that due to ts3a227e reports the jack event right away before the
notifier is registered, if headset is plugged on boot, headset button
will not get detected until headset is unplugged and plugged. This is
still an issue to be fixed.
Signed-off-by: Cheng-Yi Chiang <cychiang@chromium.org>
Link: https://lore.kernel.org/r/20191028095229.99438-1-cychiang@chromium.orgSigned-off-by: Mark Brown <broonie@kernel.org>