net: hns3: fix duplicate node in VLAN list

VLAN list should not be added duplicate VLAN node, otherwise it would
cause "add failed" when restore VLAN from VLAN list, so this patch adds
VLAN ID check before adding node into VLAN list.

Fixes: c6075b19

 ("net: hns3: Record VF vlan tables")
Signed-off-by: Guojia Liao <liaoguojia@huawei.com>
Signed-off-by: Guangbin Huang <huangguangbin2@huawei.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>