drm/imx: parallel-display: add the bridge before attaching it

Invoking drm_bridge_add() is good practice, so add it to this driver.

Link: https://lore.kernel.org/all/DDHZ5GO9MPF0.CGYTVBI74FOZ@bootlin.com
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Reviewed-by: Louis Chauvet <louis.chauvet@bootlin.com>
Link: https://patch.msgid.link/20251014-drm-bridge-alloc-imx-ipuv3-v1-2-a1bb1dcbff50@bootlin.com
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>