ASoC: tlv320aic32x4: Fix problem with first capture.

In its previous status, the first capture didn't work properly;
nothing was actually recorded from the microphone. This
behaviour was observed using a Visstrim M10 board.

In order to solve this BUG a workaround has been added that,
during the initialization process of the codec, powers on and
off the ADC.

The issue seems related to a HW BUG or some behavior that
is not documented in the datasheet.

Signed-off-by: Javier Martin <javier.martin@vista-silicon.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>