OMAPDSS: hdmi5_core: Initialize mandatory sample_order parameter

The hdmi_wp_audio_config_format() expects sample_order of struct
hdmi_audio_format to be initialized. The only allowed value is
HDMI_AUDIO_SAMPLE_LEFT_FIRST.

Signed-off-by: Jyri Sarha <jsarha@ti.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>