Treat temperature as integer, when possible

Marlin/planner.cpp

@@ -387,10 +387,7 @@ void Planner::recalculate() {
 
     float t = autotemp_min + high * autotemp_factor;
     t = constrain(t, autotemp_min, autotemp_max);
-    if (oldt > t) {
-      t *= (1 - (AUTOTEMP_OLDWEIGHT));
-      t += (AUTOTEMP_OLDWEIGHT) * oldt;
-    }
+    if (t < oldt) t = t * (1 - (AUTOTEMP_OLDWEIGHT)) + oldt * (AUTOTEMP_OLDWEIGHT);
     oldt = t;
     thermalManager.setTargetHotend(t, 0);
   }