ARM: dts: imx6sll-evk: Assign corresponding power supply for vdd3p0

On i.MX6SLL EVK board, sw2 supplies vdd3p0 LDO, this patch assigns
corresponding power supply for vdd3p0 to avoid confusion by below log:

vdd3p0: supplied by regulator-dummy

With this patch, the power supply is more accurate:

vdd3p0: supplied by SW2
Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm/boot/dts/imx6sll-evk.dts

@@ -265,6 +265,10 @@ &pwm1 {
 	status = "okay";
 };
 
+&reg_3p0 {
+	vin-supply = <&sw2_reg>;
+};
+
 &uart1 {
 	pinctrl-names = "default";
 	pinctrl-0 = <&pinctrl_uart1>;