drm/bridge: tc358767: remove tc_connector_best_encoder

drm_connector_helper_funcs.best_encoder is only needed when the
connector can have more than one encoder, and that is never the case
here.

So remove tc_connector_best_encoder.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Reviewed-by: Andrzej Hajda <a.hajda@samsung.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190528082747.3631-20-tomi.valkeinen@ti.com