formatdomain.html.in: document the new 'uuid' NVDIMM element

Signed-off-by: NDaniel Henrique Barboza <danielhb413@gmail.com>
Reviewed-by: NMichal Privoznik <mprivozn@redhat.com>

docs/formatdomain.html.in

@@ -8892,6 +8892,7 @@ qemu-kvm -net nic,model=? /dev/null
     </target>
   </memory>
   <memory model='nvdimm'>
+    <uuid>
     <source>
       <path>/tmp/nvdimm</path>
     </source>
@@ -8905,6 +8906,7 @@ qemu-kvm -net nic,model=? /dev/null
     </target>
   </memory>
   <memory model='nvdimm' access='shared'>
+    <uuid>
     <source>
       <path>/dev/dax0.0</path>
       <alignsize unit='KiB'>2048</alignsize>
@@ -8960,6 +8962,17 @@ qemu-kvm -net nic,model=? /dev/null
         </p>
       </dd>
 
+      <dt><code>uuid</code></dt>
+      <dd>
+        <p>
+          For pSeries guests, an uuid can be set to identify the
+          nvdimm module. If absent, libvirt will generate an uuid.
+          automatically. This attribute is allowed only for
+          <code>model='nvdimm'</code> for pSeries guests.
+          <span class="since">Since 6.2.0</span>
+        </p>
+      </dd>
+
       <dt><code>source</code></dt>
       <dd>
         <p>