drm/bridge: Add MAINTAINERS entry for DRM drivers for bridge chip bindings

The bindings for bridge chips should also get the same maintainers
entry so the right people get notified about bindings changes.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Neil Armstrong <narmstrong@baylibre.com>
Acked-by: Robert Foss <robert.foss@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20220308110615.1.I1f1b10daf7361feb6705f789deb680b8d7720de9@changeid