scsi: scsi_device_gets returns failure when the module is NULL.

hulk inclusion
category: bugfix
bugzilla: 189103, https://gitee.com/openeuler/kernel/issues/I7YWV4


CVE: NA

--------------------------------

when module is NULL, try_module_get return true.
But it would be better to return failure in scsi_device_get.

Signed-off-by: Zhong Jinghua <zhongjinghua@huawei.com>
Reviewed-by: Yu Kuai <yukuai3@huawei.com>
Signed-off-by: Yongqiang Liu <liuyongqiang13@huawei.com>