Max endstop pins disabled by configuration

There’s no need to ask users to uncomment Max Endstop pins when they
have them. These will be set to -1 later if the endstop option is
disabled.

Marlin/pins_MEGATRONICS_1.h

@@ -12,13 +12,13 @@
 #define X_DIR_PIN 47
 #define X_ENABLE_PIN 49
 #define X_MIN_PIN 5
-#define X_MAX_PIN -1 // 2 // Max endstops default to disabled "-1", set to commented value to enable.
+#define X_MAX_PIN 2
 
 #define Y_STEP_PIN 39 // A6
 #define Y_DIR_PIN 40 // A0
 #define Y_ENABLE_PIN 38
 #define Y_MIN_PIN 2
-#define Y_MAX_PIN -1 // 15
+#define Y_MAX_PIN 15
 
 #define Z_STEP_PIN 42 // A2
 #define Z_DIR_PIN 43 // A6