ARM: dts: sun8i: r40: Add I2S nodes

Allwinner R40 has 3 I2S controllers, compatible to those in H3. First
two are routed to pins, while third is used internally for HDMI audio.

Add nodes for all 3 I2S controllers.

Signed-off-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://lore.kernel.org/r/20210912072914.398419-3-jernej.skrabec@gmail.com