drm/bridge: get/put the bridge reference in drm_bridge_add/remove()

drm_bridge_add() adds the bridge to the global bridge_list, so take a
reference for that. Vice versa in drm_bridge_remove().

Reviewed-by: Maxime Ripard <mripard@kernel.org>
Link: https://lore.kernel.org/r/20250620-drm-bridge-alloc-getput-drm-bridge-c-v9-1-ca53372c9a84@bootlin.com


Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>