drm/omap: displays: Don't cast dssdev to panel data unnecessarily

The connect handle of the analog TV and HDMI connectors casts the dssdev
to panel data only to then access fields of the panel data that are also
present in the dssdev. Remove the cast and use dssdev directly.

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>