add rtthread.h into EFSL config.h file.

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@307 bbd45198-f89e-11dd-88c7-29a3b14d5316

filesystem/dfs/filesystems/efsl/src/include/config.h

 #ifndef __EFSL_CONFIG_H__
 #define __EFSL_CONFIG_H__
 
+/* include RT-Thread to import configuration */
+#include <rtthread.h>
+
 /* Hardware target
    ---------------