scsi: hisi_sas: Display proc_name in sysfs

The 'proc_name' entry in sysfs for hisi_sas is 'null' now because it is not
initialized in scsi_host_template. It looks like:

[root@localhost ~]# cat /sys/class/scsi_host/host2/proc_name
(null)

While the other driver's entry looks like:

linux-vnMQMU:~ # cat /sys/class/scsi_host/host0/proc_name
megaraid_sas

Link: https://lore.kernel.org/r/20200512113258.30781-1-yanaijie@huawei.com


Cc: John Garry <john.garry@huawei.com>
Cc: Xiang Chen <chenxiang66@hisilicon.com>
Acked-by: John Garry <john.garry@huawei.com>
Signed-off-by: Jason Yan <yanaijie@huawei.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>