scsi: hisi_sas: Move slot variable definition in hisi_sas_abort_task()

Each branch currently defines a slot variable independently, and it is
neater to move it to the function head.

Signed-off-by: Xingui Yang <yangxingui@huawei.com>
Signed-off-by: John Garry <john.garry@huawei.com>
Link: https://lore.kernel.org/r/1665998435-199946-3-git-send-email-john.garry@huawei.com


Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>