ASoC: dt-bindings: sun4i-spdif: Fix dma-names warning

ASoC: dt-bindings: sun4i-spdif: Fix dma-names warning

Even though the H6 compatible has been properly added, the exeption for the
number of DMA channels hasn't been updated, leading in a validation
warning.

Fix this.

Fixes: b20453031472 ("dt-bindings: sound: sun4i-spdif: Add Allwinner H6 compatible")
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Link: https://lore.kernel.org/r/20190828125209.28173-1-mripard@kernel.org
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Mark Brown <broonie@kernel.org>