dt-bindings: sound: sun4i-i2s: add Allwinner V3 I2S compatible

The I2S peripheral of the Allwinner V3 SoC is compatible with the one
found in the Allwinner H3 SoC.
This patch adds a compatible string for it.

Signed-off-by: Tobias Schramm <t.schramm@manjaro.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://lore.kernel.org/r/20210514134405.2097464-7-t.schramm@manjaro.org