dt-bindings: net: dsa: document additional Microchip KSZ8563 switch

It is a 3-Port 10/100 Ethernet Switch with 1588v2 PTP.
Signed-off-by: NRazvan Stefanescu <razvan.stefanescu@microchip.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Documentation/devicetree/bindings/net/dsa/ksz.txt

@@ -12,6 +12,7 @@ Required properties:
   - "microchip,ksz8565"
   - "microchip,ksz9893"
   - "microchip,ksz9563"
+  - "microchip,ksz8563"
 
 Optional properties: