ASoC: don't use snd_soc_write/read on twl6040

twl6040 doesn't use regmap nor reg_cache. Its write/read are done
through twl6040_reg_write/read. This driver directly calling these
functions, but sometimes using snd_soc_write/read.
As part of cleanup, snd_soc_codec_driver::write, read will be
removed soon. Then, write/read access through snd_soc_write/read
will doesn't work on this driver, since it doesn't use regmap nor
reg_cache.
This patch replace snd_soc_write/read to twl6040_write/read.

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