Prevent delay when power is already on

Fix #10410

Marlin/src/feature/power.cpp

@@ -87,6 +87,7 @@ void Power::check() {
 
 void Power::power_on() {
   lastPowerOn = millis();
+  if (!powersupply_on) {
     PSU_PIN_ON();
 
     #if HAS_TRINAMIC
@@ -94,9 +95,10 @@ void Power::power_on() {
       restore_stepper_drivers();
     #endif
   }
+}
 
 void Power::power_off() {
-  PSU_PIN_OFF();
+  if (powersupply_on) PSU_PIN_OFF();
 }
 
 #endif // AUTO_POWER_CONTROL