drm/omap: Remove HPD, detect and EDID omapdss operations

Due to the removal of several omapdrm display drivers, the omapdss HPD,
detected and EDID operations are not used anymore. Remove them and all
related code.

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/20200226112514.12455-41-laurent.pinchart@ideasonboard.com