Add the admin guide for the Cross-Thread Return Predictions vulnerability.
Signed-off-by: NTom Lendacky <thomas.lendacky@amd.com>
Message-Id: <60f9c0b4396956ce70499ae180cb548720b25c7e.1675956146.git.thomas.lendacky@amd.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>