rockchip: rk3188: add timer3 node

Add dts node for timer3.
Because of the rockchip timer can only KNOWN "dtd_rockchip_rk3368_timer"
with OF_PLATDATA enable, so we override its compatible to
"rockchip,rk3368-timer".

Signed-off-by: Kever Yang <kever.yang@rock-chips.com>
Acked-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
diff --git a/arch/arm/dts/rk3188-radxarock-u-boot.dtsi b/arch/arm/dts/rk3188-radxarock-u-boot.dtsi
index 5d650b1..26f5707 100644
--- a/arch/arm/dts/rk3188-radxarock-u-boot.dtsi
+++ b/arch/arm/dts/rk3188-radxarock-u-boot.dtsi
@@ -16,3 +16,9 @@
 	status = "okay";
 	u-boot,dm-spl;
 };
+
+&timer3 {
+	compatible = "rockchip,rk3368-timer", "rockchip,rk3288-timer";
+	u-boot,dm-spl;
+	clock-frequency = <24000000>;
+};