scsi: hisi_sas: use safe BITS_PER_BYTE for slot tag size calculation

The memory calculation for the tags bitmap should use BITS_PER_BYTE
macro instead of coincidental same value of sizeof(unsigned long).
Signed-off-by: John Garry <john.garry@huawei.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/hisi_sas/hisi_sas_main.c

@@ -1309,7 +1309,7 @@ static int hisi_sas_alloc(struct hisi_hba *hisi_hba, struct Scsi_Host *shost)
 	memset(hisi_hba->breakpoint, 0, s);
 
 	hisi_hba->slot_index_count = max_command_entries;
-	s = hisi_hba->slot_index_count / sizeof(unsigned long);
+	s = hisi_hba->slot_index_count / BITS_PER_BYTE;
 	hisi_hba->slot_index_tags = devm_kzalloc(dev, s, GFP_KERNEL);
 	if (!hisi_hba->slot_index_tags)
 		goto err_out;