ASoC: tpa6130a2: Defer SW enable from power enable

Do not enable the amplifier right after the power has been
restored to the amplifier.
The DAPM_SUPPLY widget turns on the amp early in the DAPM
power walk, and the unmuting of channel happens quite late.
Keeping the amp in SW reset state ensures better muting.
In this way the pop noise coming from other components (codec)
can be filtered out.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@nokia.com>
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Liam Girdwood <lrg@slimlogic.co.uk>