scsi: hisi_sas: devicetree: bindings: add LED feature for v2 hw

Add directly attached disk LED feature for v2 hw.

Signed-off-by: Xiaofei Tan <tanxiaofei@huawei.com>
Signed-off-by: John Garry <john.garry@huawei.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>