ath79: move ath79-clk.h include to ath79.dtsi

ath79.dtsi uses ATH79_CLK_MDIO, so the include

  <dt-bindings/clock/ath79-clk.h>

needs to be moved there.

Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>

target/linux/ath79/dts/ath79.dtsi

@@ -1,4 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0-or-later OR MIT
+
+#include <dt-bindings/clock/ath79-clk.h>
+
 / {
 	#address-cells = <1>;
 	#size-cells = <1>;