net_sched: fix a memory leak in atm_tc_init()

[ Upstream commit 306381aec7c2b5a658eebca008c8a1b666536cba ]

When tcf_block_get() fails inside atm_tc_init(),
atm_tc_put() is called to release the qdisc p->link.q.
But the flow->ref prevents it to do so, as the flow->ref
is still zero.

Fix this by moving the p->link.ref initialization before
tcf_block_get().

Fixes: 6529eaba ("net: sched: introduce tcf block infractructure")
Reported-and-tested-by:  <syzbot+d411cff6ab29cc2c311b@syzkaller.appspotmail.com>
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>