drm/bridge: analogix_dp: Add &analogix_dp_plat_data.next_bridge

drm/bridge: analogix_dp: Add &analogix_dp_plat_data.next_bridge

In order to move the panel/bridge parsing and attachmenet to the
Analogix side, add component struct drm_bridge *next_bridge to
platform data struct analogix_dp_plat_data.

The movement makes sense because the panel/bridge should logically
be positioned behind the Analogix bridge in the display pipeline.

Signed-off-by: Damon Ding <damon.ding@rock-chips.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Reviewed-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Tested-by: Heiko Stuebner <heiko@sntech.de> # rk3588
Link: https://patch.msgid.link/20260409065301.446670-2-damon.ding@rock-chips.com
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>