Fix EXTRA_FAN_SPEED

Addressing #8158

Marlin/src/Marlin.cpp

 
 #if FAN_COUNT > 0
   int16_t fanSpeeds[FAN_COUNT] = { 0 };
-  #if ENABLED(EXTRA_FAN_SPEEDS)
+  #if ENABLED(EXTRA_FAN_SPEED)
     int16_t old_fanSpeeds[FAN_COUNT],
             new_fanSpeeds[FAN_COUNT];
   #endif

Marlin/src/Marlin.h

 
 #if FAN_COUNT > 0
   extern int16_t fanSpeeds[FAN_COUNT];
-  #if ENABLED(EXTRA_FAN_SPEEDS)
+  #if ENABLED(EXTRA_FAN_SPEED)
     extern int16_t old_fanSpeeds[FAN_COUNT],
                    new_fanSpeeds[FAN_COUNT];
   #endif