scsi: hisi_sas: make local symbol host_attrs static

Fixes the following sparse warning:

drivers/scsi/hisi_sas/hisi_sas_main.c:1691:25: warning:
 symbol 'host_attrs' was not declared. Should it be static?
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Acked-by: John Garry <john.garry@huawei.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/hisi_sas/hisi_sas_main.c

@@ -1688,7 +1688,7 @@ EXPORT_SYMBOL_GPL(hisi_sas_kill_tasklets);
 struct scsi_transport_template *hisi_sas_stt;
 EXPORT_SYMBOL_GPL(hisi_sas_stt);
 
-struct device_attribute *host_attrs[] = {
+static struct device_attribute *host_attrs[] = {
 	&dev_attr_phy_event_threshold,
 	NULL,
 };