Use "& 0x3F" instead of "% 64"

Marlin/temperature.cpp

@@ -1743,9 +1743,9 @@ void Temperature::isr() {
 
     // increment slow_pwm_count only every 64th pwm_count,
     // i.e. yielding a PWM frequency of 16/128 Hz (8s).
-    if (((pwm_count >> SOFT_PWM_SCALE) % 64) == 0) {
+    if (((pwm_count >> SOFT_PWM_SCALE) & 0x3F) == 0) {
       slow_pwm_count++;
-      slow_pwm_count &= 0x7f;
+      slow_pwm_count &= 0x7F;
 
       // EXTRUDER 0
       if (state_timer_heater_0 > 0) state_timer_heater_0--;
@@ -1761,7 +1761,7 @@ void Temperature::isr() {
       #if HAS_HEATER_BED
         if (state_timer_heater_BED > 0) state_timer_heater_BED--;
       #endif
-    } // (pwm_count % 64) == 0
+    } // ((pwm_count >> SOFT_PWM_SCALE) & 0x3F) == 0
 
   #endif // SLOW_PWM_HEATERS