scsi: libsas: Use void for sas_discover_event() return code

scsi: libsas: Use void for sas_discover_event() return code

The callers of function sas_discover_event() do not check its return value.
The function also only ever returns 0, so use void instead.

Link: https://lore.kernel.org/r/1644561778-183074-2-git-send-email-chenxiang66@hisilicon.com
Reviewed-by: John Garry <john.garry@huawei.com>
Signed-off-by: Xiang Chen <chenxiang66@hisilicon.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>