Fix MKS S-Gen standard pins (#17786)

Fixes #17783

Marlin/src/pins/lpc1769/pins_MKS_SGEN.h

@@ -23,6 +23,10 @@
 
 /**
  * MKS SGen pin assignments
+ *
+ * The pins diagram can be found and the following URL:
+ * https://github.com/makerbase-mks/MKS-SGen/blob/master/Hardware/MKS%20SGEN%20V1.0_001/MKS%20SGEN%20V1.0_001%20PIN.pdf
+ *
  */
 
 #ifndef MCU_LPC1769
@@ -35,33 +39,21 @@
 #define MKS_HAS_LPC1769
 #include "../lpc1768/pins_MKS_SBASE.h"
 
-#undef E1_STEP_PIN
-#undef E1_DIR_PIN
-#undef E1_ENABLE_PIN
-
-//#undef BTN_EN1
-//#undef BTN_EN2
-//#define BTN_EN1                          P1_23  // EXP2.5
-//#define BTN_EN2                          P1_22  // EXP2.3
-
 #if HAS_TMC_UART
   /**
    * TMC2208/TMC2209 stepper drivers
-   *
-   * The shortage of pins becomes apparent.
-   * In the worst case you may have to give up the LCD.
-   * RX pins must be interrupt-capable.
    */
-  #define X_SERIAL_TX_PIN                  P4_29  // J8-2
-  #define X_SERIAL_RX_PIN                  P4_29  // J8-2
-
-  #define Y_SERIAL_TX_PIN                  P2_08  // J8-3
-  #define Y_SERIAL_RX_PIN                  P2_08  // J8-3
 
-  #define Z_SERIAL_TX_PIN                  P2_11  // J8-4
-  #define Z_SERIAL_RX_PIN                  P2_11  // J8-4
-  #define E0_SERIAL_TX_PIN                 P2_13  // J8-5
-  #define E0_SERIAL_RX_PIN                 P2_13  // J8-5
+  #define X_SERIAL_TX_PIN                  P1_22  // J8-2
+  #define X_SERIAL_RX_PIN                  P1_22  // J8-2
+  #define Y_SERIAL_TX_PIN                  P1_23  // J8-3
+  #define Y_SERIAL_RX_PIN                  P1_23  // J8-3
+  #define Z_SERIAL_TX_PIN                  P2_12  // J8-4
+  #define Z_SERIAL_RX_PIN                  P2_12  // J8-4
+  #define E0_SERIAL_TX_PIN                 P2_11  // J8-5
+  #define E0_SERIAL_RX_PIN                 P2_11  // J8-5
+  #define E1_SERIAL_TX_PIN                 P4_28  // J8-6
+  #define E1_SERIAL_RX_PIN                 P4_28  // J8-6
 
   // Reduce baud rate to improve software serial reliability
   #define TMC_BAUD_RATE 19200