Convert MicBias widgets to supply widget.

On tlv320aic3x, Mic bias power on/off shares the same register bits
with output mic bias voltage.  So, when power on mic bias, we need
reclaim it to voltage value.

Provide a new platform data so that the micbias voltage can be sent
according to board requirement. Now since tlv320aic3x codec driver
is DT aware, update dt files and functions to handle this new
"micbias-vg"  platform data.

Because of sharing of bits, when enabling the micbias, voltage also
needs to be updated. So use SND_SOC_DAPM_POST_PMU & SND_SOC_DAPM_PRE_PMD
macro to create an event to handle this.

Since micbias is converted to supply widget, updated machine drivers as
well.

This change is runtime tested on da850-evm with audio loopback
(arecord|aplay) for confirmation.
Signed-off-by: Hebbar Gururaja <gururaja.hebbar@ti.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>