KVM: SEV: move mirror status to destination of KVM_CAP_VM_MOVE_ENC_CONTEXT_FROM

Allow intra-host migration of a mirror VM; the destination VM will be
a mirror of the same ASID as the source.

Fixes: b5663931 ("KVM: SEV: Add support for SEV intra host migration")
Reviewed-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20211123005036.2954379-8-pbonzini@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>