Rename file or directory.
FRESULT f_rename ( const char* OldName, // Pointer to old object name const char* NewName // Pointer to new object name );
Rename a file or directory and can move it to other directory. This function is not supported in read-only configuration or minimization level of >= 1.
Note: In this revision, moving any directory to other directory collapses the file system.
    // Rename file or directory
    f_rename("oldname.txt", "newname.txt");
    // Rename and move file to other directory simultaneously
    f_rename("oldname.txt", "dir1/newname.txt");