ASoC: STA529: Add support for STA529 Audio Codec

The STA529 is a digital stereo class-D audio amplifier. It includes an
audio DSP, an ST proprietary high-efficiency class-D driver and CMOS
power output stage. It is intended for high-efficiency
digital-to-power-audio conversion for portable applications.

Signed-off-by: Rajeev Kumar <rajeev-dlh.kumar@st.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>