🐛 Allow SKR Pro CONTROLLER_FAN_PIN override

Followup to #22411

Marlin/src/pins/stm32f4/pins_BTT_SKR_PRO_common.h

   #define E0_AUTO_FAN_PIN               FAN1_PIN
 #endif
 
-#if ENABLED(USE_CONTROLLER_FAN) && HOTENDS < 2
+#if !defined(CONTROLLER_FAN_PIN) && ENABLED(USE_CONTROLLER_FAN) && HOTENDS < 2
   #define CONTROLLER_FAN_PIN                PE6   // Fan2
 #else
   #define FAN2_PIN                          PE6   // Fan2