OMAPDSS: Remove all references to obsolete HDMI audio callbacks

In new model these callbacks are obsolete since the ASoC component
drivers are integrated into the HDMI drivers and no callbacks are
needed anymore.

Signed-off-by: Jyri Sarha <jsarha@ti.com>
Reviewed-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>