ARM: imx6sl-evk: set swbst_reg as vbus's parent reg

USB vbus 5V is from PMIC SWBST, so set swbst_reg as vbus's
parent reg, it fixed a bug that the voltage of vbus is incorrect
due to swbst_reg is disabled after boots up.

Cc: stable@vger.kernel.org
Signed-off-by: Peter Chen <peter.chen@freescale.com>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>

arch/arm/boot/dts/imx6sl-evk.dts

@@ -52,6 +52,7 @@ reg_usb_otg1_vbus: regulator@0 {
 			regulator-max-microvolt = <5000000>;
 			gpio = <&gpio4 0 0>;
 			enable-active-high;
+			vin-supply = <&swbst_reg>;
 		};
 
 		reg_usb_otg2_vbus: regulator@1 {
@@ -62,6 +63,7 @@ reg_usb_otg2_vbus: regulator@1 {
 			regulator-max-microvolt = <5000000>;
 			gpio = <&gpio4 2 0>;
 			enable-active-high;
+			vin-supply = <&swbst_reg>;
 		};
 
 		reg_aud3v: regulator@2 {