drm/imx: ldb: switch to imx_legacy_bridge / drm_bridge_connector

drm/imx: ldb: switch to imx_legacy_bridge / drm_bridge_connector

Use the imx_legacy bridge driver instead of handlign display modes via
the connector node.

All existing usecases already support attaching using
the DRM_BRIDGE_ATTACH_NO_CONNECTOR flag, while the imx_legacy bridge
doesn't support creating connector at all. Switch to
drm_bridge_connector at the same time.

Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
Tested-by: Chris Healy <cphealy@gmail.com>
Tested-by: Philipp Zabel <p.zabel@pengutronix.de> # on imx6q-nitrogen6x
Link: https://patchwork.freedesktop.org/patch/msgid/20240602-drm-imx-cleanup-v3-10-e549e2a43100@linaro.org
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>