ARM: sti: Add STiH407 reset controller support.

This patch adds the reset controller DT nodes for the powerdown,
 softreset and picophy controllers.
Signed-off-by: Peter Griffin <peter.griffin@linaro.org>
Signed-off-by: Maxime Coquelin <maxime.coquelin@st.com>

arch/arm/boot/dts/stih407.dtsi

@@ -8,6 +8,7 @@
  */
 #include "stih407-clock.dtsi"
 #include "stih407-pinctrl.dtsi"
+#include <dt-bindings/reset-controller/stih407-resets.h>
 / {
 	#address-cells = <1>;
 	#size-cells = <1>;
@@ -63,6 +64,21 @@ soc {
 		ranges;
 		compatible = "simple-bus";
 
+		powerdown: powerdown-controller {
+			compatible = "st,stih407-powerdown";
+			#reset-cells = <1>;
+		};
+
+		softreset: softreset-controller {
+			compatible = "st,stih407-softreset";
+			#reset-cells = <1>;
+		};
+
+		picophyreset: picophyreset-controller {
+			compatible = "st,stih407-picophyreset";
+			#reset-cells = <1>;
+		};
+
 		syscfg_sbc: sbc-syscfg@9620000 {
 			compatible = "st,stih407-sbc-syscfg", "syscon";
 			reg = <0x9620000 0x1000>;