dt-bindings: net: sparx5: do not require phys when RGMII is used

LAN969x has 2 dedicated RGMII ports, so regular SERDES lanes are not used
for RGMII.

So, lets not require phys to be defined when any of the rgmii phy-modes are
set.

Signed-off-by: Robert Marko <robert.marko@sartura.hr>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://patch.msgid.link/20260115114021.111324-11-robert.marko@sartura.hr
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Documentation/devicetree/bindings/net/microchip,sparx5-switch.yaml

@@ -151,10 +151,23 @@ properties:
 
         required:
           - reg
-          - phys
           - phy-mode
           - microchip,bandwidth
 
+        if:
+          not:
+            properties:
+              phy-mode:
+                contains:
+                  enum:
+                    - rgmii
+                    - rgmii-id
+                    - rgmii-rxid
+                    - rgmii-txid
+        then:
+          required:
+            - phys
+
         oneOf:
           - required:
               - phy-handle