dt-bindings: net: cdns,macb: add sam9x7 ethernet interface

Add documentation for sam9x7 ethernet interface.
Signed-off-by: Varshini Rajendran <varshini.rajendran@microchip.com>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20240223172228.671553-1-varshini.rajendran@microchip.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

Documentation/devicetree/bindings/net/cdns,macb.yaml

@@ -59,6 +59,11 @@ properties:
           - cdns,gem                  # Generic
           - cdns,macb                 # Generic
 
+      - items:
+          - enum:
+              - microchip,sam9x7-gem     # Microchip SAM9X7 gigabit ethernet interface
+          - const: microchip,sama7g5-gem # Microchip SAMA7G5 gigabit ethernet interface
+
   reg:
     minItems: 1
     items: