ASoC: mxs-sgtl5000: Remove unneeded fields from snd_soc_dai_link

It makes no sense to hardcode the I2C bus into the codec_name field.

cpu_dai_name and platform_name are also overwritten later in
mxs_sgtl5000_probe_dt().

So remove the three fields, as mxs platform is dt-only platform.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Acked-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>