Implement support for the KVM_X86_SEV_VM and KVM_X86_SEV_ES_VM virtual
machine types, and the KVM_SEV_INIT2 function of KVM_MEMORY_ENCRYPT_OP.
These replace the KVM_SEV_INIT and KVM_SEV_ES_INIT functions, and have
several advantages:
- sharing the initialization sequence with SEV-SNP and TDX
- allowing arguments including the set of desired VMSA features
- protection against invalid use of KVM_GET/SET_* ioctls for guests
with encrypted state
If the KVM_X86_SEV_VM and KVM_X86_SEV_ES_VM types are not supported,
fall back to KVM_SEV_INIT and KVM_SEV_ES_INIT (which use the
default x86 VM type).
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>