ARM: dts: kirkwood: Fix sound DAI cells for OpenRD clients
A previous commit changed the '#sound-dai-cells' property for the
kirkwood audio controller from 1 to 0 in the kirkwood.dtsi file,
but did not update the corresponding 'sound-dai' property in the
kirkwood-openrd-client.dts file.
This created a mismatch, causing a dtbs_check validation error where
the dts provides one cell (<&audio0 0>) while the .dtsi expects zero.
Remove the extraneous cell from the 'sound-dai' property to fix the
schema validation warning and align with the updated binding.