scsi: Drop useless null test in scsi_unit_attention() req was created by scsi_req_alloc(), which initializes req->dev to a value it dereferences. req->dev isn't changed anywhere else. Therefore, req->dev can't be null. Drop the useless null test; it spooks Coverity. Signed-off-by: Markus Armbruster <armbru@redhat.com>