scsi: hisi_sas: Delete some unused callbacks

mainline inclusion
from mainline-master
commit 2843d2fb
category: bugfix
bugzilla: 175270
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=2843d2fb42254ac443c83e5e0b97e1cae6b7a4de

------------------------------------------------------------------------

The debugfs code has been relocated to v3 hw driver, so delete unused
struct hisi_sas_hw function pointers snapshot_{prepare, restore}.

Link: https://lore.kernel.org/r/1617709711-195853-2-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>
Reviewed-by: Ouyangdelong <ouyangdelong@huawei.com>
Signed-off-by: Nifujia <nifujia1@hisilicon.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>