ASoC: sgtl5000: Pass the required '#sound-dai-cells'

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

arch/arm/boot/dts/imx6ul-geam.dtb: Warning (sound_dai_property): /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 improve the documentation.

Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Mark Brown <broonie@kernel.org>