arm64: dts: rockchip: add i2s_8ch_2 and i2s_8ch_3 to rk3308

These are I2S engines internally connected to the built-in audio codec.

Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Link: https://lore.kernel.org/r/20240305-rk3308-audio-codec-v4-6-312acdbe628f@bootlin.com


Signed-off-by: Heiko Stuebner <heiko@sntech.de>