drm/omap: dss: Remove .set_hdmi_mode() and .set_infoframe() operations

The omapdss_hdmi_ops .set_hdmi_mode() and .set_infoframe() operations
operations are not used anymore, remove them.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Tested-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200226112514.12455-37-laurent.pinchart@ideasonboard.com