dt-bindings: net: lan966x: Extend with the ptp external interrupt.

Extend dt-bindings for lan966x with ptp external interrupt. This is
generated when an external 1pps signal is received on the ptp pin.
Signed-off-by: Horatiu Vultur <horatiu.vultur@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/devicetree/bindings/net/microchip,lan966x-switch.yaml

@@ -39,6 +39,7 @@ properties:
       - description: frame dma based extraction
       - description: analyzer interrupt
       - description: ptp interrupt
+      - description: ptp external interrupt
 
   interrupt-names:
     minItems: 1
@@ -47,6 +48,7 @@ properties:
       - const: fdma
       - const: ana
       - const: ptp
+      - const: ptp-ext
 
   resets:
     items: