s390/lcs: Fix return type of lcsstartxmit()
This is an automated ID intended to aid in discovery of potential security vulnerabilities. The actual impact and attack plausibility have not yet been proven. This ID is fixed in Linux Kernel version v4.9.337 by commit 7b4da3fcd513b8e67823eb80da37aad99b3339c1. For more details please see the references link.