Documentation/bindings: net: marvell-pp2: add the link interrupt

A link interrupt can be described. Document this valid interrupt name.
Signed-off-by: NAntoine Tenart <antoine.tenart@free-electrons.com>
Tested-by: NMarcin Wojtas <mw@semihalf.com>
Reviewed-by: NAndrew Lunn <andrew@lunn.ch>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Documentation/devicetree/bindings/net/marvell-pp2.txt

@@ -44,7 +44,7 @@ Optional properties (port):
 - interrupt-names: if more than a single interrupt for rx is given, must
                    be the name associated to the interrupts listed. Valid
                    names are: "tx-cpu0", "tx-cpu1", "tx-cpu2", "tx-cpu3",
-		   "rx-shared".
+		   "rx-shared", "link".
 - marvell,system-controller: a phandle to the system controller.
 
 Example for marvell,armada-375-pp2: