ASoC: sun8i-codec: Convert to use SND_SOC_DAPM_AIF_IN

Update the driver to use SND_SOC_DAPM_AIF_IN instead of
SND_SOC_DAPM_DAC.
Rename the interface's widgets to be more precise on which slot
the interface is connected.

Signed-off-by: Mylène Josserand <mylene.josserand@free-electrons.com>
Signed-off-by: Mark Brown <broonie@kernel.org>