ASoC: remove unused comment

`type` parameter is not longer used in `snd_soc_codec_set_cache_io`,
so remove this line.

Signed-off-by: Lu Guanqun <guanqun.lu@intel.com>
Acked-by: Liam Girdwood <lrg@ti.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>