vfs: use sys/dirent.h from newlib

The dirent.h shipped with the risc-v compiler lacks `extern "C"`
declartion and causes linkage declartion conflict when included in C++
files. Use the dirent.h from newlib only to avoid this issue.

components/vfs/include/esp_vfs.h

@@ -29,7 +29,7 @@
 #include <sys/time.h>
 #include <sys/termios.h>
 #include <sys/poll.h>
-#include <dirent.h>
+#include <sys/dirent.h>
 #include <string.h>
 #include "sdkconfig.h"