ASoC: tpa6130a2: Use snd soc volsw functions

Use snd_soc_{info,get,put}_volsw instead of custom volume functions

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
[koike: port for upstream]
Signed-off-by: Helen Koike <helen.koike@collabora.co.uk>
[On N900]
Tested-By: Sebastian Reichel <sre@kernel.org>
Reviewed-By: Sebastian Reichel <sre@kernel.org>
Signed-off-by: Mark Brown <broonie@kernel.org>