This patch implements LED feature of directly attached disk for v3 hw.

In fact, this hw has created an SGPIO component for LED feature, and we can
control LEDs just by internal registers.
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>