bnxt_en: Fixed the VF link status after a link state change

The VF link state can be changed via the 'ip link set' cmd.
Currently, the new link state does not take effect immediately.

The fix is for the PF to send a link change async event to the
designated VF after a VF link state change.  This async event will
trigger the VF to update the link status.

Signed-off-by: Eddie Wai <eddie.wai@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>