ARM: dts: stm32: Repair PMIC configuration on AV96

The vdd PMIC buck regulator was misconfigured, which caused instability
of the board and malfunction of high-speed interfaces, like the RGMII.
Configure the PMIC correctly to repair these problems. Also add missing
Enpirion regulator for the IO voltage into the DT.
Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Alexandre Torgue <alexandre.torgue@st.com>
Cc: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Cc: Maxime Coquelin <mcoquelin.stm32@gmail.com>
Cc: Patrice Chotard <patrice.chotard@st.com>
Cc: Patrick Delaunay <patrick.delaunay@st.com>
Cc: linux-stm32@st-md-mailman.stormreply.com
To: linux-arm-kernel@lists.infradead.org
Signed-off-by: Alexandre Torgue <alexandre.torgue@st.com>

arch/arm/boot/dts/stm32mp157a-avenger96.dts

@@ -77,6 +77,17 @@ led6 {
 			default-state = "off";
 		};
 	};
+
+	/* Enpirion EP3A8LQI U2 on the DHCOR */
+	vdd_io: regulator-buck-io {
+		compatible = "regulator-fixed";
+		regulator-name = "buck-io";
+		regulator-min-microvolt = <1800000>;
+		regulator-max-microvolt = <1800000>;
+		regulator-always-on;
+		regulator-boot-on;
+		vin-supply = <&vdd>;
+	};
 };
 
 &ethernet0 {
@@ -166,8 +177,8 @@ vdd_ddr: buck2 {
 
 			vdd: buck3 {
 				regulator-name = "vdd";
-				regulator-min-microvolt = <3300000>;
-				regulator-max-microvolt = <3300000>;
+				regulator-min-microvolt = <2900000>;
+				regulator-max-microvolt = <2900000>;
 				regulator-always-on;
 				regulator-initial-mode = <0>;
 				regulator-over-current-protection;
@@ -245,6 +256,7 @@ vbus_otg: pwr_sw1 {
 				regulator-name = "vbus_otg";
 				interrupts = <IT_OCP_OTG 0>;
 				interrupt-parent = <&pmic>;
+				regulator-active-discharge = <1>;
 			};
 
 			vbus_sw: pwr_sw2 {
@@ -275,7 +287,7 @@ &iwdg2 {
 };
 
 &pwr_regulators {
-	vdd-supply = <&vdd>;
+	vdd-supply = <&vdd_io>;
 	vdd_3v3_usbfs-supply = <&vdd_usb>;
 };