scsi: hisi_sas: Add debugfs file structure for port

Create a file structure which was used to save the memory address and phy
pointer for port at debugfs. This structure is bound to the corresponding
debugfs file, it can help callback function of debugfs file to get what it
need.

Link: https://lore.kernel.org/r/1571926105-74636-10-git-send-email-john.garry@huawei.com


Signed-off-by: Luo Jiaxing <luojiaxing@huawei.com>
Signed-off-by: John Garry <john.garry@huawei.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>