Update sd_sim.c

bsp/simulator/drivers/sd_sim.c

-#include <rtthread.h>
 #include <stdio.h>
-#ifdef _WIN32
 #include <stdlib.h>
 #include <string.h>
-#endif
+
+#include <rtthread.h>
 #include <dfs_def.h>
 
 // #define SD_TRACE     rt_kprintf