s390/boot: fix absolute zero lowcore corruption on boot
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 v5.15.68 by commit 4b198c41d736c1c4c4974fd53cd03d632abdb6be, it was introduced in version v3.18 by commit a62bc0739253939d6fce40d51d92412252a9bb55. For more details please see the references link.