arm64: dts: allwinner: a64: Add pinmux nodes for AIF2/AIF3

Now that the sun8i-codec driver supports AIF2 and AIF3, boards can use
them in DAI links. Add the necessary pinmux nodes.

Signed-off-by: Samuel Holland <samuel@sholland.org>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://lore.kernel.org/r/20210430035859.3487-5-samuel@sholland.org