Shrink debug code in Stopwatch and disable by default

Marlin/stopwatch.cpp

 #include "stopwatch.h"
 
 Stopwatch::Stopwatch() {
-   this->reset();
- }
+  this->reset();
+}
 
 void Stopwatch::stop() {
-  if (DEBUGGING(INFO)) SERIAL_ECHOLNPGM("Stopwatch::stop()");
+  #if ENABLED(DEBUG_STOPWATCH)
+    debug(PSTR("stop"));
+  #endif
+
   if (!this->isRunning()) return;
 
   this->status = STPWTCH_STOPPED;
 }
 
 void Stopwatch::pause() {
-  if (DEBUGGING(INFO)) SERIAL_ECHOLNPGM("Stopwatch::pause()");
+  #if ENABLED(DEBUG_STOPWATCH)
+    debug(PSTR("pause"));
+  #endif
+
   if (!this->isRunning()) return;
 
   this->status = STPWTCH_PAUSED;
 }
 
 void Stopwatch::start() {
-  if (DEBUGGING(INFO)) SERIAL_ECHOLNPGM("Stopwatch::start()");
+  #if ENABLED(DEBUG_STOPWATCH)
+    debug(PSTR("start"));
+  #endif
+
   if (this->isRunning()) return;
 
   if (this->isPaused()) this->accumulator = this->duration();
 }
 
 void Stopwatch::reset() {
-  if (DEBUGGING(INFO)) SERIAL_ECHOLNPGM("Stopwatch::reset()");
+  #if ENABLED(DEBUG_STOPWATCH)
+    debug(PSTR("reset"));
+  #endif
 
   this->status = STPWTCH_STOPPED;
   this->startTimestamp = 0;
   return (((this->isRunning()) ? millis() : this->stopTimestamp)
           - this->startTimestamp) / 1000 + this->accumulator;
 }
+
+#if ENABLED(DEBUG_STOPWATCH)
+
+  void Stopwatch::debug(const char func[]) {
+    if (DEBUGGING(INFO)) {
+      SERIAL_ECHOPGM("Stopwatch::");
+      serialprintPGM(func);
+      SERIAL_ECHOLNPGM("()");
+    }
+  }
+
+#endif

Marlin/stopwatch.h

 #ifndef STOPWATCH_H
 #define STOPWATCH_H
 
+#include "macros.h"
+
+// Print debug messages with M111 S2 (Uses 156 bytes of PROGMEM)
+//#define DEBUG_STOPWATCH
+
 enum StopwatchStatus {
-  STPWTCH_STOPPED = 0x0,
-  STPWTCH_RUNNING = 0x1,
-  STPWTCH_PAUSED  = 0x2
+  STPWTCH_STOPPED,
+  STPWTCH_RUNNING,
+  STPWTCH_PAUSED
 };
 
 /**
      * @return uint16_t
      */
     uint16_t duration();
+
+    #if ENABLED(DEBUG_STOPWATCH)
+
+      /**
+       * @brief Prints a debug message
+       * @details Prints a simple debug message "Stopwatch::function"
+       */
+      static void debug(const char func[]);
+
+    #endif
 };
 
 #endif //STOPWATCH_H