[NET_SCHED]: Eliminate qdisc_tree_lock

Since we're now holding the rtnl during the entire dump operation, we
can remove qdisc_tree_lock, whose only purpose is to protect dump
callbacks from concurrent changes to the qdisc tree.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --cc include/net/pkt_sched.h
Simple merge

diff --cc net/sched/cls_api.c
Simple merge

diff --cc net/sched/sch_api.c
Simple merge

diff --cc net/sched/sch_generic.c
Simple merge