fdts: stm32mp1: fix vdd_usb on stm32mp15 boards

vdd_usb must not be present unless vdda1v8 is present. So, as vdda1v8 is
disabled during standby, vdd_usb cannot be kept on during suspend.

Signed-off-by: Amelie Delaunay <amelie.delaunay@st.com>
Change-Id: I49d9683fd2ca7f89cf17cc3147585fc6b8916388

fdts/stm32mp15xx-dkx.dtsi

@@ -472,7 +472,7 @@
 
 &vdd_usb {
 	standby-ddr-sr {
-		regulator-on-in-suspend;
+		regulator-off-in-suspend;
 	};
 	standby-ddr-off {
 		regulator-off-in-suspend;

fdts/stm32mp15xx-edx.dtsi

@@ -475,7 +475,7 @@
 
 &vdd_usb {
 	standby-ddr-sr {
-		regulator-on-in-suspend;
+		regulator-off-in-suspend;
 	};
 	standby-ddr-off {
 		regulator-off-in-suspend;