net: hns3: add support for VF modify VLAN filter state

Previously, there is hardware limitation for VF to modify
the VLAN filter state, and the VLAN filter state is default
enabled. Now the limitation has been removed in some device,
so add capability flag to check whether the device supports
modify VLAN filter state. If flag on, user will be able to
modify the VLAN filter state by ethtool -K.
VF needs to send mailbox to request the PF to modify the VLAN
filter state for it.

Signed-off-by: Jian Shen <shenjian15@huawei.com>
Signed-off-by: Huazhong Tan <tanhuazhong@huawei.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>