media: dt-binding: media: hynix,hi846: use $defs/port-base port description

This fixes "make dt_binding_check":

    Documentation/devicetree/bindings/media/i2c/hynix,hi846.example.dt.yaml:
camera@20: port:endpoint: Unevaluated properties are not allowed
('link-frequencies', 'data-lanes' were unexpected)
    From schema: Documentation/devicetree/bindings/media/i2c/hynix,hi846.yaml

[Sakari Ailus: Reword commit message]

Fixes: f3ce7200 ("media: dt-bindings: media: document SK Hynix Hi-846 MIPI CSI-2 8M pixel sensor")
Reported-by: NGeert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: NMartin Kepplinger <martin.kepplinger@puri.sm>
Reviewed-by: NLaurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: NRob Herring <robh@kernel.org>
Signed-off-by: NSakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@kernel.org>

Documentation/devicetree/bindings/media/i2c/hynix,hi846.yaml

@@ -49,7 +49,8 @@ properties:
     description: Definition of the regulator used for the VDDD power supply.
 
   port:
-    $ref: /schemas/graph.yaml#/properties/port
+    $ref: /schemas/graph.yaml#/$defs/port-base
+    unevaluatedProperties: false
 
     properties:
       endpoint: