MAINTAINERS: Add include/drm/drm_bridge.h to DRM DRIVERS FOR BRIDGE CHIPS

Appropriate maintainers should be suggested for changes to the
include/drm/drm_bridge.h header file, so add the header file to the
'DRM DRIVERS FOR BRIDGE CHIPS' section.

Signed-off-by: Liu Ying <victor.liu@nxp.com>
Acked-by: Robert Foss <robert.foss@linaro.org>
Acked-by: Neil Armstrong <neil.armstrong@linaro.org>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230313055951.2997299-1-victor.liu@nxp.com