Chitu V6 - Stepper Z2 pins (#18683)

Marlin/src/pins/stm32f1/pins_CHITU3D_V6.h

@@ -73,6 +73,10 @@
 #define Z_STEP_PIN                          PB9
 #define Z_DIR_PIN                           PE0
 
+#define Z2_ENABLE_PIN                       PF3
+#define Z2_STEP_PIN                         PF5
+#define Z2_DIR_PIN                          PF1
+
 #define E0_ENABLE_PIN                       PB8
 #define E0_STEP_PIN                         PB4
 #define E0_DIR_PIN                          PB5