drm/bridge: panel: Fix typo in drm_panel_bridge_add docs

Fix the 'manged' typo with 'managed' in the drm_panel_bridge_add
kernel-doc documentation.

Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191218121223.30181-1-enric.balletbo@collabora.com