When binding to an ipv6 address, it calls ipv6_chk_addr() to check if
this address is on any dev. If a socket binds to a l3mdev but no dev
is passed to do this check, all l3mdev and slaves will be skipped and
the check will fail.

This patch is to pass the bound_dev to make sure the devices under the
same l3mdev can be returned in ipv6_chk_addr(). When the bound_dev is
not a l3mdev or l3slave, l3mdev_master_dev_rcu() will return NULL in
__ipv6_chk_addr_and_flags(), it will keep compitable with before when
NULL dev was passed.
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>