arm: dts: am335x: enable prcm_clocks auto binding

Adding the 'simple-bus' compatible string to the prcm_clocks node will
allow its automatic binding.

Signed-off-by: Dario Binacchi <dariobin@libero.it>
diff --git a/arch/arm/dts/am33xx-u-boot.dtsi b/arch/arm/dts/am33xx-u-boot.dtsi
index 78f5e2c..2426ece 100644
--- a/arch/arm/dts/am33xx-u-boot.dtsi
+++ b/arch/arm/dts/am33xx-u-boot.dtsi
@@ -9,3 +9,7 @@
 		u-boot,dm-pre-reloc;
 	};
 };
+
+&prcm_clocks {
+	compatible = "simple-bus";
+};