ASoC: hdmi-codec: Rework to support more controls

We're going to add more controls to support the IEC958 output, so let's
rework the control registration a bit to support more of them.

Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Acked-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20210525132354.297468-4-maxime@cerno.tech