scsi: hisi_sas: make local symbol host_attrs static

scsi: hisi_sas: make local symbol host_attrs static

BugLink: http://bugs.launchpad.net/bugs/1756094
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>
(cherry picked from commit 1e15feacb9d3743ca0b314a6daf8cc59c90b1046)
Signed-off-by: Manoj Iyer <manoj.iyer@canonical.com>
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>