ASoC: sun8i-codec: Update mixer to use SOC_DAPM_DOUBLE

Update the driver to use the new SOC_DAPM_DOUBLE definition
on the digital DAC mixer.
Update the names accordingly as, when they are shared, the
controls are not prefixed with the widget's name anymore.

Signed-off-by: Mylène Josserand <mylene.josserand@free-electrons.com>
Acked-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Mark Brown <broonie@kernel.org>