OMAPDSS: HDMI: Remove ASoC codec

Remove the ASoC OMAP HDMI audio codec. The goal of removing the codec
is to, in subsequent patches, give way to the implementation of the HDMI
audio support using the DSS device driver audio interface. This
approach will expose the HDMI audio functionality to any interested entity.

In a separate patch, ASoC will use this new approach to expose HDMI audio
to ALSA.

Signed-off-by: Ricardo Neri <ricardo.neri@ti.com>