Refresh user space standard output

In the original user space output implementation, we would display
several chess board in seqeunce. However, we only want to see the
latest result of chess board, we use ascii escape code to refresh the
stardard output every time before we plot the chess board out.

Author: vax-r

kmldrv-user.c

@@ -133,6 +133,7 @@ int main(int argc, char *argv[])
             listen_keyboard_handler();
         } else if (read_attr && FD_ISSET(device_fd, &readset)) {
             FD_CLR(device_fd, &readset);
+            printf("\033[H\033[J"); /* ASCII escape code to clear the screen */
             read(device_fd, display_buf, DRAWBUFFER_SIZE);
             printf("%s", display_buf);
         }