net-next: When a bond have a massive amount of VLANs with IPv6 addresses, performance of changing link state, attaching a VRF, changing an IPv6 address, etc. go down dramtically.

The source of most of the slow down is the `dev_addr_lists.c` module,
which mainatins a linked list of HW addresses.
When using IPv6, this list grows for each IPv6 address added on a
VLAN, since each IPv6 address has a multicast HW address associated with
it.

When performing any modification to the involved links, this list is
traversed many times, often for nothing, all while holding the RTNL
lock.

Instead, this patch adds an auxilliary rbtree which cuts down
traversal time significantly.

Performance can be seen with the following script:

	#!/bin/bash
	ip netns del test || true 2>/dev/null
	ip netns add test

	echo 1 | ip netns exec test tee /proc/sys/net/ipv6/conf/all/keep_addr_on_down > /dev/null

	set -e

	ip -n test link add foo type veth peer name bar
	ip -n test link add b1 type bond
	ip -n test link add florp type vrf table 10

	ip -n test link set bar master b1
	ip -n test link set foo up
	ip -n test link set bar up
	ip -n test link set b1 up
	ip -n test link set florp up

	VLAN_COUNT=1500
	BASE_DEV=b1

	echo Creating vlans
	ip netns exec test time -p bash -c "for i in \$(seq 1 $VLAN_COUNT);
	do ip -n test link add link $BASE_DEV name foo.\$i type vlan id \$i; done"

	echo Bringing them up
	ip netns exec test time -p bash -c "for i in \$(seq 1 $VLAN_COUNT);
	do ip -n test link set foo.\$i up; done"

	echo Assiging IPv6 Addresses
	ip netns exec test time -p bash -c "for i in \$(seq 1 $VLAN_COUNT);
	do ip -n test address add dev foo.\$i 2000::\$i/64; done"

	echo Attaching to VRF
	ip netns exec test time -p bash -c "for i in \$(seq 1 $VLAN_COUNT);
	do ip -n test link set foo.\$i master florp; done"

On an Intel(R) Xeon(R) CPU E5-2650 v3 @ 2.30GHz machine, the performance
before the patch is (truncated):

	Creating vlans
	real 108.35
	Bringing them up
	real 4.96
	Assiging IPv6 Addresses
	real 19.22
	Attaching to VRF
	real 458.84

After the patch:

	Creating vlans
	real 5.59
	Bringing them up
	real 5.07
	Assiging IPv6 Addresses
	real 5.64
	Attaching to VRF
	real 25.37

Cc: David S. Miller <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Lu Wei <luwei32@huawei.com>
Cc: Xiongfeng Wang <wangxiongfeng2@huawei.com>
Cc: Taehee Yoo <ap420073@gmail.com>
Signed-off-by: Gilad Naaman <gnaaman@drivenets.com>
Signed-off-by: David S. Miller <davem@davemloft.net>