drm/omap: Remove .get_timings() operation from display connectors

The analog TV, DVI and HDMI connectors all report timing information
through the .get_timings() information.

For analog TV outputs the information is queried from the encoder, so
the operation is unused. Remove it.

For HDMI outputs the display pipeline provides EDID capability, so the
operation is unused as well. Remove it.

For DVI outputs the operation is also unused if the pipeline provides
EDID capability. Otherwise (when the DDC bus is not connected) we
shouldn't hardcode a single mode, but instead report no mode and let the
KMS core add default modes. This is achieved by removing the operation.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>