scsi: hisi_sas: downgrade refclk message

The message to inform that the controller has no refclk
is currently at warning level, which is unnecessary, so
downgrade to debug.

Signed-off-by: John Garry <john.garry@huawei.com>
Reviewed-by: Xiang Chen <chenxiang66@hisilicon.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>