scsi: hisi_sas: Add ability to have multiple debugfs dumps

We use the module parameter debugfs_dump_count to manage the upper limit of
the memory block for multiple dumps.

Link: https://lore.kernel.org/r/1571926105-74636-17-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>