[SCSI] scsi_transport_iscsi: Add flash node mgmt support
This patch allows iscsiadm to manage iSCSI target information stored on
adapter flash on per host basis.
The sysfs entries will look as cited below:
/sys/bus/iscsi_flashnode/devices/flashnode_sess-<host_no>:<flashnode_id>/<session attrs>
/sys/bus/iscsi_flashnode/devices/flashnode_conn-<host_no>:<flashnode_id>:<conn_id>/<conn attrs>