ARM: dts: imx6ul-isiot: Pass the required '#sound-dai-cells'

DTC now warns about missing #sound-dai-cells:

/sound/simple-audio-card,codec: Missing property '#sound-dai-cells' in
node /soc/aips-bus@2100000/i2c@21a0000/codec@a or bad phandle
(referred from sound-dai[0])

Pass the required '#sound-dai-cells' property to fix it.

Reported-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>