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 v5.15.86 by commit 5ad774fb823c24bbeb21a15a67103ea7a6f5b928. For more details please see the references link.