arm64: zynqmp: Update Copyright years to 2020

Trivial change.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
diff --git a/arch/arm/dts/zynqmp-clk.dtsi b/arch/arm/dts/zynqmp-clk.dtsi
index c9464ec..82eac56 100644
--- a/arch/arm/dts/zynqmp-clk.dtsi
+++ b/arch/arm/dts/zynqmp-clk.dtsi
@@ -2,7 +2,7 @@
 /*
  * Clock specification for Xilinx ZynqMP
  *
- * (C) Copyright 2015 - 2018, Xilinx, Inc.
+ * (C) Copyright 2015 - 2020, Xilinx, Inc.
  *
  * Michal Simek <michal.simek@xilinx.com>
  */