dt-bindings: net: bcmgenet: Add BCM2711 support

The BCM2711 has some modifications to the GENET v5. So add this SoC
specific compatible.
Suggested-by: NFlorian Fainelli <f.fainelli@gmail.com>
Signed-off-by: NStefan Wahren <wahrenst@gmx.net>
Reviewed-by: NFlorian Fainelli <f.fainelli@gmail.com>
Acked-by: NRob Herring <robh@kernel.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Documentation/devicetree/bindings/net/brcm,bcmgenet.txt

@@ -2,7 +2,7 @@
 
 Required properties:
 - compatible: should contain one of "brcm,genet-v1", "brcm,genet-v2",
-  "brcm,genet-v3", "brcm,genet-v4", "brcm,genet-v5".
+  "brcm,genet-v3", "brcm,genet-v4", "brcm,genet-v5", "brcm,bcm2711-genet-v5".
 - reg: address and length of the register set for the device
 - interrupts and/or interrupts-extended: must be two cells, the first cell
   is the general purpose interrupt line, while the second cell is the