CNV-62285: Move vTPM note to docs

Author: erpeters157

modules/virt-adding-vtpm-to-vm.adoc

@@ -11,6 +11,11 @@ Adding a virtual Trusted Platform Module (vTPM) device to a virtual machine
 (VM) allows you to run a VM created from a Windows 11 image without a physical
 TPM device. A vTPM device also stores secrets for that VM.
 
+[IMPORTANT]
+====
+When you add a virtual Trusted Platform Module (vTPM) device to a Windows VM, it is important to make the vTPM device persistent. The BitLocker Drive is encrypted successfully and the encryption system check passes even if the vTPM device is not persistent. If the vTPM device is not persistent, it is discarded on shutdown.
+====
+
 .Prerequisites
 * You have installed the OpenShift CLI (`oc`).