ASoC: tlv320aic3x: Use snd_soc_read and snd_soc_write

Start phasing out aic3x_read_reg_cache, aic3x_write_reg_cache, aic3x_read and
aic3x_write calls in order to switch to soc-cache helpers.

This patch replaces aic3x_read_reg_cache and aic3x_write with snd_soc_read
and snd_soc_write. This is basically null-op since .read and .write in
soc_codec_dev_aic3x points to aic3x_read_reg_cache and aic3x_write.
Signed-off-by: Jarkko Nikula <jhnikula@gmail.com>
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Liam Girdwood <lrg@slimlogic.co.uk>