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 v5.10.163 by commit ebc3c77785dc8b5b626309c0032a38fbb139287a. For more details please see the references link.