OMAP4: DSS2: HDMI: Implement ASoC Codec driver for HDMI audio

Implement an ASoC Codec Driver to handle audio configuration. The
implementation offers an interface for audio configuration and
control to be exposed to ALSA while hidding the HDMI details.

The ASoC driver supports the Basic Audio configuration as described
in CEA-861-D: 2-channel linear PCM with 32, 44.1 and 48kHz sample
rates and 16 bits/sample. It additionally supports 24 bit/sample
in 32-bit words.

Signed-off-by: Ricardo Neri <ricardo.neri@ti.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>