[SCSI] bnx2fc: Handle NETDEV_UNREGISTER for vlan devices

Since the driver holds the reference for vlan netdev, the reference has to be
released by the driver when the vlan device is removed. Driver handles this in
NETDEV_UNREGISTER event.

Signed-off-by: Bhanu Prakash Gollapudi <bprakash@broadcom.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>