dt-bindings: clock: lan966x: Extend for clock gate support

Allow to add an optional resource to be able to access the clock gate
registers.

Signed-off-by: Horatiu Vultur <horatiu.vultur@microchip.com>
Acked-by: Rob Herring <robh@kernel.org>
Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Link: https://lore.kernel.org/r/20211103085102.1656081-3-horatiu.vultur@microchip.com

Documentation/devicetree/bindings/clock/microchip,lan966x-gck.yaml

@@ -19,7 +19,10 @@ properties:
     const: microchip,lan966x-gck
 
   reg:
-    maxItems: 1
+    minItems: 1
+    items:
+      - description: Generic clock registers
+      - description: Optional gate clock registers
 
   clocks:
     items: