OMAP: DSS2: HDMI: split hdmi_core_ddc_edid

Split the DDC initialization off from hdmi_core_ddc_edid() into a
separate function hdmi_core_ddc_init(). This cleans up the
implementation.

Cc: Mythri P K <mythripk@ti.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>