i40e: fix use-after-free in i40e_sync_filters_subtask()

Using ifconfig command to delete the ipv6 address will cause
the i40e network card driver to delete its internal mac_filter and
i40e_service_task kernel thread will concurrently access the mac_filter.
These two processes are not protected by lock
so causing the following use-after-free problems.

 print_address_description+0x70/0x360
 ? vprintk_func+0x5e/0xf0
 kasan_report+0x1b2/0x330
 i40e_sync_vsi_filters+0x4f0/0x1850 [i40e]
 i40e_sync_filters_subtask+0xe3/0x130 [i40e]
 i40e_service_task+0x195/0x24c0 [i40e]
 process_one_work+0x3f5/0x7d0
 worker_thread+0x61/0x6c0
 ? process_one_work+0x7d0/0x7d0
 kthread+0x1c3/0x1f0
 ? kthread_park+0xc0/0xc0
 ret_from_fork+0x35/0x40

Allocated by task 2279810:
 kasan_kmalloc+0xa0/0xd0
 kmem_cache_alloc_trace+0xf3/0x1e0
 i40e_add_filter+0x127/0x2b0 [i40e]
 i40e_add_mac_filter+0x156/0x190 [i40e]
 i40e_addr_sync+0x2d/0x40 [i40e]
 __hw_addr_sync_dev+0x154/0x210
 i40e_set_rx_mode+0x6d/0xf0 [i40e]
 __dev_set_rx_mode+0xfb/0x1f0
 __dev_mc_add+0x6c/0x90
 igmp6_group_added+0x214/0x230
 __ipv6_dev_mc_inc+0x338/0x4f0
 addrconf_join_solict.part.7+0xa2/0xd0
 addrconf_dad_work+0x500/0x980
 process_one_work+0x3f5/0x7d0
 worker_thread+0x61/0x6c0
 kthread+0x1c3/0x1f0
 ret_from_fork+0x35/0x40

Freed by task 2547073:
 __kasan_slab_free+0x130/0x180
 kfree+0x90/0x1b0
 __i40e_del_filter+0xa3/0xf0 [i40e]
 i40e_del_mac_filter+0xf3/0x130 [i40e]
 i40e_addr_unsync+0x85/0xa0 [i40e]
 __hw_addr_sync_dev+0x9d/0x210
 i40e_set_rx_mode+0x6d/0xf0 [i40e]
 __dev_set_rx_mode+0xfb/0x1f0
 __dev_mc_del+0x69/0x80
 igmp6_group_dropped+0x279/0x510
 __ipv6_dev_mc_dec+0x174/0x220
 addrconf_leave_solict.part.8+0xa2/0xd0
 __ipv6_ifa_notify+0x4cd/0x570
 ipv6_ifa_notify+0x58/0x80
 ipv6_del_addr+0x259/0x4a0
 inet6_addr_del+0x188/0x260
 addrconf_del_ifaddr+0xcc/0x130
 inet6_ioctl+0x152/0x190
 sock_do_ioctl+0xd8/0x2b0
 sock_ioctl+0x2e5/0x4c0
 do_vfs_ioctl+0x14e/0xa80
 ksys_ioctl+0x7c/0xa0
 __x64_sys_ioctl+0x42/0x50
 do_syscall_64+0x98/0x2c0
 entry_SYSCALL_64_after_hwframe+0x65/0xca

Fixes: 41c445ff

 ("i40e: main driver core")
Signed-off-by: Di Zhu <zhudi2@huawei.com>
Signed-off-by: Rui Zhang <zhangrui182@huawei.com>
Tested-by: Gurucharan G <gurucharanx.g@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>