ASoC: tlv320dac33: fix regression by adding back .read/.write

commit c4305af4 ("ASoC: use internal reg_cache on tlv320dac33")
removed .read/.write from driver, but it might breaks non-regmap
driver, because ALSA SoC framework might call it.

To fix this regression, this patch back .read/.write

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Mark Brown <broonie@kernel.org>