dt-bindings: sound: sun4i-spdif: Add Allwinner H6 compatible

Allwinner H6 has a SPDIF controller with an increase of the fifo
size and a sligher difference in memory mapping compare to H3/A64.

This make it not compatible with the previous generation.

Introduce a specific bindings for H6 SoC.

Signed-off-by: Clément Péron <peron.clem@gmail.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>
Signed-off-by: Mark Brown <broonie@kernel.org>