ExtUI: Fix fan wrapping around from 0 to 100 (#12987)

Marlin/src/lcd/extensible_ui/ui_api.cpp

 
   void setTargetFan_percent(const float value, const fan_t fan) {
     if (fan < FAN_COUNT)
-      thermalManager.set_fan_speed(fan - FAN0, map(value, 0, 100, 0, 255));
+      thermalManager.set_fan_speed(fan - FAN0, map(clamp(value, 0, 100), 0, 100, 0, 255));
   }
 
   void setFeedrate_percent(const float value) {