drm/omap: dss: Cleanup DSS ports on initialisation failure

When the DSS initialises its output DPI and SDI ports, failures don't
clean up previous successfully initialised ports. This can lead to
resource leak or memory corruption. Fix it.

Reported-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
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/20200226112514.12455-22-laurent.pinchart@ideasonboard.com