docs: Change TD example policy to 0x10000000

The definition of BIT0 in policy element comes from TDX spec, but it makes
confusion for some customers whether 0 or 1 activates debug:

  1. We know that "off-TD debug mode" basically means debug from outside the
     TD --> 1 activates debug.
  2. But when a customer is not aware of the term "off-TD debug" it is very
     easy to misinterpret this as "TD debug mode off" --> 1 deactivates debug.

Given that the policy example uses "0x10000001", the second interpretation
even becomes more likely, because a customer may assume that security by
default is applied in the example.

Thus, change the policy in example configuration to "0x10000000" and update
BIT0 definition to be more explicit.

Suggested-by: Fuhry Benny <benny.fuhry@intel.com>
Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>

docs/formatdomain.rst

@@ -9834,7 +9834,7 @@ Example configuration:
    <domain>
      ...
      <launchSecurity type='tdx'>
-       <policy>0x10000001</policy>
+       <policy>0x10000000</policy>
        <mrConfigId>xxx</mrConfigId>
        <mrOwner>xxx</mrOwner>
        <mrOwnerConfig>xxx</mrOwnerConfig>
@@ -9855,7 +9855,9 @@ Example configuration:
    ====== ====================================================================================
    Bit(s) Description
    ====== ====================================================================================
-   0      Guest TD runs in off-TD debug mode when set
+   0      Activate off-TD debug when set, i.e., activate debug from outside the TD. Its VCPU
+          state and private memory are accessible by the host VMM.
+          Deactivate off-TD debug when clear, i.e., deactivate debug from outside the TD.
    1:27   reserved
    28     Disable EPT violation conversion to #VE on guest TD access of PENDING pages when set
    29:63  reserved