arm64: dts: rockchip: fix I2S conflict on rk3399-rock-pi-4

Based on the board schematics at
https://dl.radxa.com/rockpi4/docs/hw/rockpi4/rockpi_4c_v12_sch_20200620.pdf


on page 14:
Only two channels of I2S are connected and the extra
I2S pins are in conflict with other functions like USB power.

Signed-off-by: Vicente Bergas <vicencb@gmail.com>
Link: https://lore.kernel.org/r/20201201154132.1286-3-vicencb@gmail.com


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