This patch adds support to configure VF link properties.
The options are auto, enable, and disable. Even if the PF
is down, the communication between VFs will be normal
if the VFs are set to enable. The commands are as follows:

'ip link set <pf> vf <vf_id> state <auto|enable|disable>'
change the VF status

'ip link show'
show the setting status
Signed-off-by: Yufeng Mo <moyufeng@huawei.com>
Signed-off-by: Huazhong Tan <tanhuazhong@huawei.com>
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>