net: hns3: fix RMW issue for VLAN filter switch

According to the user manual, the ingress and egress VLAN filter
are configured at the same time. Currently, hclge_init_vlan_config()
and hclge_set_vlan_spoofchk() will both change the VLAN filter
switch. So it's necessary to read the old configuration before
modifying it.

Fixes: 22044f95 ("net: hns3: add support for spoof check setting")
Signed-off-by: Jian Shen <shenjian15@huawei.com>
Signed-off-by: Huazhong Tan <tanhuazhong@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>