Add support for MKS Robin board (#12650)

Implement initial support for MKS Robin (STM32F103ZET6) board.
Custom build script is used to generate encrypted firmware compatible with original MSK Robin bootloader (i.e. safe firmware update from SD card and possibility to go back to original close-source firmware).

Marlin/src/HAL/HAL_STM32F1/HAL.cpp

@@ -43,7 +43,7 @@
 // --------------------------------------------------------------------------
 
 #define __I
-#define __IO
+#define __IO volatile
  typedef struct
  {
    __I  uint32_t CPUID;                   /*!< Offset: 0x000 (R/ )  CPUID Base Register                                   */
@@ -105,7 +105,7 @@ uint8 adc_pins[] = {
     TEMP_0_PIN,
   #endif
   #if HAS_TEMP_ADC_1
-    TEMP_1_PIN
+    TEMP_1_PIN,
   #endif
   #if HAS_TEMP_ADC_2
     TEMP_2_PIN,
@@ -175,6 +175,24 @@ static void NVIC_SetPriorityGrouping(uint32_t PriorityGroup) {
 // Public functions
 // --------------------------------------------------------------------------
 
+//
+// Leave PA11/PA12 intact if USBSerial is not used
+//
+#if SERIAL_USB
+  namespace wirish { namespace priv {
+    #if SERIAL_PORT > 0
+      #if SERIAL_PORT2
+        #if SERIAL_PORT2 > 0
+          void board_setup_usb(void) {}
+        #endif
+      #else
+        void board_setup_usb(void) {}
+      #endif
+    #endif
+  } }
+#endif
+
+
 void HAL_init(void) {
   NVIC_SetPriorityGrouping(0x3);
 }