tools/counter: Makefile: Remove lingering 'include' directories on make clean

`make` creates 'include' directories where necessary, so remove them as
appropriate on `make clean`.

Signed-off-by: Rong Tao <rongtao@cestc.cn>
Link: https://lore.kernel.org/r/tencent_F85E314661100B0CE2845EB27E2E2F558C09@qq.com/
Signed-off-by: William Breathitt Gray <william.gray@linaro.org>

tools/counter/Makefile

@@ -40,6 +40,7 @@ $(OUTPUT)counter_example: $(COUNTER_EXAMPLE)
 clean:
 	rm -f $(ALL_PROGRAMS)
 	rm -rf $(OUTPUT)include/linux/counter.h
+	rmdir -p $(OUTPUT)include/linux
 	find $(or $(OUTPUT),.) -name '*.o' -delete -o -name '\.*.d' -delete
 
 install: $(ALL_PROGRAMS)