net: macb: Add tsu_clk to device tree

Signed-off-by: NRafal Ozieblo <rafalo@cadence.com>
Acked-by: NRob Herring <robh@kernel.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Documentation/devicetree/bindings/net/macb.txt

@@ -22,6 +22,7 @@ Required properties:
 	Required elements: 'pclk', 'hclk'
 	Optional elements: 'tx_clk'
 	Optional elements: 'rx_clk' applies to cdns,zynqmp-gem
+	Optional elements: 'tsu_clk'
 - clocks: Phandles to input clocks.
 
 Optional properties for PHY child node: