arm64: dts: allwinner: a64: Allow using multiple codec DAIs

Increase #sound-dai-cells on the digital codec to allow using the other
DAIs provided by the codec for AIF2 and AIF3.

Signed-off-by: Samuel Holland <samuel@sholland.org>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://lore.kernel.org/r/20210430035859.3487-4-samuel@sholland.org