ARM: dts: Use OF graph for DP to panel connection in exynos5800-peach-pi

The DT binding for the Exynos DRM Display Port (DP) driver isn't consistent
since it uses a phandle to describe the connection between the DP port and
the display panel but uses the OF graph ports and endpoints to describe the
connection betwen the DP port, a bridge chip and the panel.

The Exynos DP driver and the DT binding have been changed to allow also to
describe the DP port to panel connection using ports / endpoints (OF graph)
so this patch changes the Exynos5800 Peach Pi DT to make it consistent with
the Exynos5420 Peach Pit that has a eDP to LVDS chip and uses OF graph too.

Signed-off-by: Javier Martinez Canillas <javier@osg.samsung.com>
Reviewed-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>