ARM: dts: rockchip: add #sound-dai-cells to hdmi node on rk3128

'#sound-dai-cells' is required to properly interpret
the list of DAI specified in the 'sound-dai' property,
so add them to the 'hdmi' node for 'rk3128.dtsi'.

Signed-off-by: Johan Jonker <jbx6244@gmail.com>
Link: https://lore.kernel.org/r/9d0fabb0-70b0-4b4b-ac7c-389b1c7afe20@gmail.com


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