bnxt_en: Handle VF_CFG_CHANGE event from firmware.

When the VF driver gets this event, the VF configuration has changed (such
as default VLAN).  The VF driver will initiate a silent reset to pick up
the new configuration.

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