OMAPDSS: hdmi: Make hdmi_mode_has_audio() more user friedly

Make hdmi_mode_has_audio() more user friedly by taking hdmi_config as
parameter.

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