🐛 Fix some BTT SKR2 pins (#22558)

Marlin/src/pins/stm32f4/pins_BTT_SKR_V2_0_common.h

@@ -153,13 +153,6 @@
   #define POWER_LOSS_PIN                    PC15  // PWRDET
 #endif
 
-//
-// NeoPixel LED
-//
-#ifndef NEOPIXEL_PIN
-  #define NEOPIXEL_PIN                      PE6
-#endif
-
 //
 // Control pin of driver/heater/fan power supply
 //
@@ -511,6 +504,13 @@
   #endif
 #endif
 
+//
+// NeoPixel LED
+//
+#ifndef NEOPIXEL_PIN
+  #define NEOPIXEL_PIN                      PE6
+#endif
+
 //
 // WIFI
 //

ini/stm32f4.ini

@@ -207,6 +207,7 @@ build_flags                 = ${stm_flash_drive.build_flags}
                               -DUSE_USBHOST_HS -DUSE_USB_HS_IN_FS
                               -DUSBD_IRQ_PRIO=5 -DUSBD_IRQ_SUBPRIO=6
                               -DHSE_VALUE=8000000U -DHAL_SD_MODULE_ENABLED
+                              -DPIN_SERIAL3_RX=PD_9 -DPIN_SERIAL3_TX=PD_8
 
 #
 # BigTreeTech SKR V2.0 (STM32F407VGT6 ARM Cortex-M4) with USB Media Share Support