drm/bridge: ti-sn65dsi86: Group code in sections

Reorganize the functions in sections, related to connector operations,
bridge operations, AUX adapter, GPIO controller and probe & remove.

This prepares for proper support of DRM_BRIDGE_ATTACH_NO_CONNECTOR that
will add more functions, to ensure that the code will stay readable.

No functional change intended.
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Robert Foss <robert.foss@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20210624000304.16281-6-laurent.pinchart+renesas@ideasonboard.com