ARM: omap4.dtsi: Add audio related parametes to hdmi node

Adds HDMI audio sDMA properties.

Signed-off-by: Jyri Sarha <jsarha@ti.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Acked-by: Tony Lindgren <tony@atomide.com>