add N32G4XM_STB board support

add nationz N32G4XM_STB board support

board/N32G4XM_STB/BSP/Src/mcu_init.c

@@ -0,0 +1,35 @@
+#include "mcu_init.h"
+
+void board_init(void)
+{
+    log_init();
+}
+
+#ifdef USE_FULL_ASSERT
+
+/**
+ * @brief  Reports the name of the source file and the source line number
+ *         where the assert_param error has occurred.
+ * @param file pointer to the source file name
+ * @param line assert_param error line source number
+ */
+void assert_failed(const uint8_t* expr, const uint8_t* file, uint32_t line)
+{
+    /* User can add his own implementation to report the file name and line number,
+       ex: printf("Wrong parameters value: file %s on line %d\r\n", file, line) */
+
+    /* Infinite loop */
+    while (1)
+    {
+    }
+}
+
+#endif
+
+/**
+ * @}
+ */
+
+/**
+ * @}
+ */