ASoC: add ak4554 driver

ak4554 is very simple DA/AD converter which has no setting register.
Note that it has hard coded asymmetric data format
playback : SND_SOC_DAIFMT_RIGHT_J
capture  : SND_SOC_DAIFMT_LEFT_J
This driver has single DAI and doesn't have set_fmt.

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