scsi: be2iscsi: Move VLAN code to common iface_set_param

VLAN tag is L2 construct, move VLAN code out from configuring IP.
Rearrange and rename the APIs to make it consistent.
Replace ENOSYS with EPERM.

Signed-off-by: Jitendra Bhivare <jitendra.bhivare@broadcom.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>