sch_dsmark: use correct func name in print messages

In dsmark_drop(), the function name printed by pr_debug
is "dsmark_reset", correct it to "dsmark_drop" by using
__func__ .

BTW, replace the other function names with __func__ .

Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>