Merge tag 'kvm-s390-master-5.9-1' of...

Merge tag 'kvm-s390-master-5.9-1' of git://git.kernel.org/pub/scm/linux/kernel/git/kvms390/linux into kvm-master

KVM: s390: add documentation for KVM_CAP_S390_DIAG318

diag318 code was merged in 5.9-rc1, let us add some
missing documentation