drm/bridge: analogix_dp: Apply panel_bridge helper

drm/bridge: analogix_dp: Apply panel_bridge helper

In order to unify the handling of the panel and bridge, apply
panel_bridge helpers for Analogix DP driver. With this patch, the
bridge support will also become available.

The following changes have ben made:
- Apply plane_bridge helper to wrap the panel as the bridge.
- Remove the explicit panel APIs calls, which can be replaced with
  the automic bridge APIs calls wrapped by the panel.
- Remove the unnecessary analogix_dp_bridge_get_modes().

Signed-off-by: Damon Ding <damon.ding@rock-chips.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Tested-by: Heiko Stuebner <heiko@sntech.de> # rk3588
Link: https://patch.msgid.link/20260413132551.1049307-9-damon.ding@rock-chips.com
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>