Add COUNT macro and apply

Marlin/Sd2PinMap.h

@@ -19,6 +19,8 @@
  */
 // Warning this file was generated by a program.
 #include "Marlin.h"
+#include "macros.h"
+
 #ifdef SDSUPPORT
 
 #ifndef Sd2PinMap_h
@@ -385,7 +387,7 @@ static const pin_map_t digitalPinMap[] = {
 #error unknown chip
 #endif  // defined(__AVR_ATmega1280__)
 //------------------------------------------------------------------------------
-static const uint8_t digitalPinCount = sizeof(digitalPinMap)/sizeof(pin_map_t);
+static const uint8_t digitalPinCount = COUNT(digitalPinMap);
 
 uint8_t badPinNumber(void)
   __attribute__((error("Pin number is too large or not a constant")));