scsi: hisi_sas: Make sg_tablesize consistent value

Sht->sg_tablesize is set in the driver, and it will be assigned to
shost->sg_tablesize in SCSI mid-layer. So it is not necessary to assign
shost->sg_table one more time in the driver.

In addition to the change, change each scsi_host_template.sg_tablesize
to HISI_SAS_SGE_PAGE_CNT instead of SG_ALL.

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