OMAPDSS: HDMI: Add an audio configuration function

The generic HDMI driver does not need to know about the specific
settings of a given IP. Hence, it just passes the audio configuration
and the IP library parses such configuration and sets the IP
accordingly. This patch introduces an IP-specific audio configuration
function.

Also, this patch implements the audio config function for OMAP4. The
DMA, format and core config functions are no longer exposed to the
generic HDMI driver as they are IP-specific.

The audio configuration function caters for 16-bit through 24-bit
audio samples with sample rates from 32kHz and up to 192kHz as well
as up to 8 audio channels.

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