When a link is enslave to bond, it need to set the interface down first.
This makes the slave remove mac multicast address 33:33:00:00:00:01(The
IPv6 multicast address ff02::1 is kept even when the interface down). When
bond set the slave up, ipv6_mc_up() was not called due to commit c2edacf8
("bonding / ipv6: no addrconf for slaves separately from master").

This is not an issue before we adding the lladdr target feature for bonding,
as the mac multicast address will be added back when bond interface up and
join group ff02::1.

But after adding lladdr target feature for bonding. When user set a lladdr
target, the unsolicited NA message with all-nodes multicast dest will be
dropped as the slave interface never add 33:33:00:00:00:01 back.

Fix this by calling ipv6_mc_up() to add 33:33:00:00:00:01 back when
the slave interface up.
Reported-by: LiLiang <liali@redhat.com>
Fixes: 5e1eeef6 ("bonding: NS target should accept link local address")
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>