Use NUM_DIGITAL_PINS instead of custom DIO_COUNT

Marlin/Marlin_main.cpp

     }
 
     // Get the range of pins to test or watch
-    int first_pin = 0, last_pin = DIO_COUNT - 1;
+    int first_pin = 0, last_pin = NUM_DIGITAL_PINS - 1;
     if (code_seen('P')) {
       first_pin = last_pin = code_value_byte();
-      if (first_pin > DIO_COUNT - 1) return;
+      if (first_pin > NUM_DIGITAL_PINS - 1) return;
     }
 
     bool ignore_protection = code_seen('I') ? code_value_bool() : false;

Marlin/pinsDebug.h

  *
  */
 
-// How many DIO pins are defined?
-#ifdef DIO85_PIN
-//  #define DIO_COUNT 86
-  #define DIO_COUNT 70  // digitalRead and other Arduino IDE routines only know about pins 0 through 69
-#elif defined(DIO53_PIN)
-  #define DIO_COUNT 54
-#elif defined(DIO47_PIN)
-  #define DIO_COUNT 48
-#elif defined(DIO31_PIN)
-  #define DIO_COUNT 32
-#elif defined(DIO21_PIN)
-  #define DIO_COUNT 22
-#endif
-
 bool endstop_monitor_flag = false;
 
 #define  NAME_FORMAT "%-28s"   // one place to specify the format of all the sources of names
   #if PIN_EXISTS(DIGIPOTSS)
     PIN_SAY(DIGIPOTSS_PIN);
   #endif
-  #if defined(DIO_COUNT) && DIO_COUNT >= 0
-    PIN_SAY(DIO_COUNT);
-  #endif
   #if defined(DOGLCD_A0) && DOGLCD_A0 >= 0
     PIN_SAY(DOGLCD_A0);
   #endif