MAINTAINERS: Update Maintainers of DRM Bridge Drivers

Add myself as co-maintainer of DRM Bridge Drivers. Repository
commit access has already been granted.

https://gitlab.freedesktop.org/freedesktop/freedesktop/-/issues/338



Signed-off-by: Robert Foss <robert.foss@linaro.org>
Acked-by: Neil Armstrong <narmstrong@baylibre.com>
Acked-by: Maxime Ripard <maxime@cerno.tech>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Andrzej Hajda <a.hajda@samsung.com>
Cc: Neil Armstrong <narmstrong@baylibre.com>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Jonas Karlman <jonas@kwiboo.se>
Cc: Andrzej Hajda <a.hajda@samsung.com>
Cc: Jernej Škrabec <jernej.skrabec@siol.net>
Cc: Daniel Vetter <daniel@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20210325145154.1433060-1-robert.foss@linaro.org