KVM: SEV: Init target VMCBs in sev_migrate_from

KVM: SEV: Init target VMCBs in sev_migrate_from

The target VMCBs during an intra-host migration need to correctly setup
for running SEV and SEV-ES guests. Add sev_init_vmcb() function and make
sev_es_init_vmcb() static. sev_init_vmcb() uses the now private function
to init SEV-ES guests VMCBs when needed.

Fixes: 0b020f5af092 ("KVM: SEV: Add support for SEV-ES intra host migration")
Fixes: b56639318bb2 ("KVM: SEV: Add support for SEV intra host migration")
Signed-off-by: Peter Gonda <pgonda@google.com>
Cc: Marc Orr <marcorr@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: kvm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Message-Id: <20220623173406.744645-1-pgonda@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>