drm/bridge: ti-sn65dsi86: Wrap panel with panel-bridge

To simplify interfacing with the panel, wrap it in a panel-bridge and
let the DRM bridge helpers handle chaining of operations.

This also prepares for support of DRM_BRIDGE_ATTACH_NO_CONNECTOR, which
requires all components in the display pipeline to be represented by
bridges.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Reviewed-by: Jagan Teki <jagan@amarulasolutions.com>
Signed-off-by: Robert Foss <robert.foss@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20210624000304.16281-5-laurent.pinchart+renesas@ideasonboard.com