scsi: scsi_device_gets returns failure when the module is NULL.

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


CVE: NA

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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>
Signed-off-by: Li Lingfeng <lilingfeng3@huawei.com>