Restructuring the twl4030 codec's DAPM routing to be able to handle the power
sequences correctly.

The twl4030 codec internal implementation have this order:
DAC -> Analog PGA -> Mixer/Mux

While the ASoC framework expects the following order:
DAC -> Mixer -> Analog PGA

This patch moves the Analog PGA handling from SND_SOC_DAPM_PGA to _MIXER and
adds two levels of mixer to handle the digital and analog loopback
functionality.

Now the analog loopback does not powers on any of the DACs.
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@nokia.com>
Tested-by: Anuj Aggarwal <anuj.aggarwal@ti.com>
Tested-by: Jarkko Nikula <jhnikula@gmail.com>
Tested-by: Misael Lopez Cruz  <x0052729@ti.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>