The ti-sn65dsi86 driver shouldn't hand-roll its own bridge
connector. It should use the normal drm_bridge_connector. Let's switch
to do that, removing all of the custom code.

NOTE: this still _doesn't_ implement DRM_BRIDGE_ATTACH_NO_CONNECTOR
support for ti-sn65dsi86 and that would still be a useful thing to do
in the future. It was attempted in the past [1] but put on the back
burner. However, unless we instantly change ti-sn65dsi86 fully from
not supporting DRM_BRIDGE_ATTACH_NO_CONNECTOR at all to _only_
supporting DRM_BRIDGE_ATTACH_NO_CONNECTOR then we'll still need a bit
of time when we support both. This is a better way to support the old
way where the driver hand rolls things itself.

A new notes about the implementation here:
* When using the drm_bridge_connector the connector should be created
  after all the bridges, so we change the ordering a bit.
* I'm reasonably certain that we don't need to do anything to "free"
  the new drm_bridge_connector. If drm_bridge_connector_init() returns
  success then we know drm_connector_init() was called with the
  `drm_bridge_connector_funcs`. The `drm_bridge_connector_funcs` has a
  .destroy() that does all the cleanup. drm_connector_init() calls
  __drm_mode_object_add() with a drm_connector_free() that will call
  the .destroy().
* I'm also reasonably certain that I don't need to "undo" the
  drm_bridge_attach() if drm_bridge_connector_init() fails. The
  "detach" function is private and other similar code doesn't try to
  undo the drm_bridge_attach() in error cases. There's also a comment
  indicating the lack of balance at the top of drm_bridge_attach().

[1] https://lore.kernel.org/r/20210920225801.227211-4-robdclark@gmail.comSigned-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220204161245.v2.1.I3ab26b7f197cc56c874246a43e57913e9c2c1028@changeid