arm: dts: kirkwood: fix error in #sound-dai-cells size

dtc now gives the following warning:

arch/arm/boot/dts/kirkwood-t5325.dtb: Warning (sound_dai_property): /sound/simple-audio-card,cpu:sound-dai: property size (4) too small for cell size 1

The binding documentation gives no indication what the cell size should
be (which should be fixed too), so just assume 0 is fine as that is what
the consumer has.

Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Andrew Lunn <andrew@lunn.ch>
Cc: Gregory Clement <gregory.clement@free-electrons.com>
Cc: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Signed-off-by: Rob Herring <robh@kernel.org>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>