add new line to /proc/*/loadavg snprintf format.

fs/procfs/fs_procfsproc.c

@@ -754,7 +754,7 @@ static ssize_t proc_loadavg(FAR struct proc_file_s *procfile,
     }
 
   linesize = procfs_snprintf(procfile->line, STATUS_LINELEN,
-                             "%3" PRId32 ".%01" PRId32 "%%",
+                             "%3" PRId32 ".%01" PRId32 "%%\n",
                              intpart, fracpart);
   copysize = procfs_memcpy(procfile->line, linesize, buffer, buflen,
                            &offset);