In revision 0x20, we use vlan id != 0 to check whether a vlan tag
has been offloaded, so vlan id 0 is not supported.

In revision 0x21, rx buffer descriptor adds two bits to indicate
whether one or more vlan tags have been offloaded, so vlan id 0
is valid now.

This patch seperates the handle for vlan id 0, add vlan id 0 support
for revision 0x21.

Fixes: 5b5455a9 ("net: hns3: Add STRP_TAGP field support for hardware revision 0x21")
Signed-off-by: Jian Shen <shenjian15@huawei.com>
Signed-off-by: Salil Mehta <salil.mehta@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>