ASoC: tpa6130a2: Add DAPM support

Add DAPM support and updated rx51 accordingly.
As a consequence:
- the exported function tpa6130a2_stereo_enable is not needed anymore
- the mutex is dealt in the DAPM
- the power state is tracked by the DAPM

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
[koike: port for upstream]
Signed-off-by: Helen Koike <helen.koike@collabora.co.uk>
Tested-by: Sebastian Reichel <sre@kernel.org>
Reviewed-by: Sebastian Reichel <sre@kernel.org>
Signed-off-by: Mark Brown <broonie@kernel.org>