ASoC: io: Clean up snd_soc_codec_set_cache_io()

Now that all users have been converted to regmap and the config.reg_bits
and config.val_bits can be setted by each user through regmap core API.
So these two params are redundant here.
Signed-off-by: NXiubo Li <Li.Xiubo@freescale.com>
Signed-off-by: NMark Brown <broonie@linaro.org>

sound/soc/soc-io.c

@@ -88,16 +88,11 @@ int snd_soc_codec_set_cache_io(struct snd_soc_codec *codec,
 			       int addr_bits, int data_bits,
 			       enum snd_soc_control_type control)
 {
-	struct regmap_config config;
 	int ret;
 
-	memset(&config, 0, sizeof(config));
 	codec->write = hw_write;
 	codec->read = hw_read;
 
-	config.reg_bits = addr_bits;
-	config.val_bits = data_bits;
-
 	switch (control) {
 	case SND_SOC_REGMAP:
 		/* Device has made its own regmap arrangements */