We don't consistenly document the default value next to the option
listing, but we do have a list of defaults here, so let's keep it up to
date.

Cherry picked from Linux commit 4f07510df2e8c47fd65b8ffaaf6c5d334d59d598.
Signed-off-by: NBrian Norris <computersforpeace@gmail.com>
Reviewed-by: NThomas Huth <thuth@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>