drm/bridge: lvds-codec: Simplify panel DT node localisation

The probe function needs to get ahold of the panel device tree
node, and it achieves that by using a combination of
of_graph_get_port_by_id, of_get_child_by_name, and
of_graph_get_remote_port_parent. We can achieve the same goal
by replacing those calls with a call to of_graph_get_remote_node
these days.

Signed-off-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1573660292-10629-8-git-send-email-fabrizio.castro@bp.renesas.com