scsi: hisi_sas: Alloc debugfs snapshot buffer memory for all registers

scsi: hisi_sas: Alloc debugfs snapshot buffer memory for all registers

This patch allocates snapshot memory for global reg, port regs, CQ, DQ,
IOST, ITCT.

When we fail to allocate memory for some registers, we free the memory
and set hisi_sas_debugfs_enable as 0 to stop loading debugfs from running.

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>