Previously, VF updates its link status every second by send query command
to PF in periodic service task. If link stats of PF is changed, VF may
need at most one second to update its link status.

To reduce delay of link status between PF and VFs, PF actively push its
link status to VFs when its link status is updated. And to let VF know
PF supports this new feature, the link status changed mailbox command
adds one bit to indicate it.
Signed-off-by: NGuangbin Huang <huangguangbin2@huawei.com>
Signed-off-by: NHuazhong Tan <tanhuazhong@huawei.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>