NEOPIXEL overridable on BTT SKR (#20797)

Marlin/src/pins/lpc1769/pins_BTT_SKR_E3_TURBO.h

 #endif
 
 // LED driving pin
-#define NEOPIXEL_PIN                       P1_24
+#ifndef NEOPIXEL_PIN
+  #define NEOPIXEL_PIN                     P1_24
+#endif
 
 //
 // Power Loss Detection

Marlin/src/pins/stm32f1/pins_BTT_SKR_CR6.h

 // Misc. Functions
 //
 #define LED_CONTROL_PIN                     PA13
-#define NEOPIXEL_PIN                        PA8
+
+#ifndef NEOPIXEL_PIN
+  #define NEOPIXEL_PIN                      PA8
+#endif

Marlin/src/pins/stm32f1/pins_BTT_SKR_MINI_E3_V1_2.h

 
 #define BOARD_INFO_NAME "BTT SKR Mini E3 V1.2"
 
-#define NEOPIXEL_PIN                        PC7   // LED driving pin
+#ifndef NEOPIXEL_PIN
+  #define NEOPIXEL_PIN                      PC7   // LED driving pin
+#endif
 
 /**
  * TMC2208/TMC2209 stepper drivers

Marlin/src/pins/stm32f1/pins_BTT_SKR_MINI_E3_V2_0.h

 // Release PA13/PA14 (led, usb control) from SWD pins
 #define DISABLE_DEBUG
 
-#define NEOPIXEL_PIN                       PA8   // LED driving pin
+#ifndef NEOPIXEL_PIN
+  #define NEOPIXEL_PIN                     PA8   // LED driving pin
+#endif
 
-#define PS_ON_PIN                          PC13  // Power Supply Control
+#ifndef PS_ON_PIN
+  #define PS_ON_PIN                        PC13  // Power Supply Control
+#endif
 
 #define FAN1_PIN                           PC7