docs: Tweak PCI controller model documentation

Instead of first listing the models on their own, and then
listing them again grouped by the libvirt release they were
introduced in, have a single list.
Signed-off-by: NAndrea Bolognani <abologna@redhat.com>
Reviewed-by: NJohn Ferlan <jferlan@redhat.com>

docs/formatdomain.html.in

@@ -3935,19 +3935,30 @@
 ...</pre>
 
     <p>
-      PCI controllers have an optional <code>model</code> attribute with
-      possible values <code>pci-root</code>, <code>pcie-root</code>,
-      <code>pcie-root-port</code>, <code>pci-bridge</code>,
-      <code>dmi-to-pci-bridge</code>, <code>pcie-switch-upstream-port</code>,
-      <code>pcie-switch-downstream-port</code>, <code>pci-expander-bus</code>,
-      or <code>pcie-expander-bus</code>.  (pci-root and
-      pci-bridge <span class="since">since 1.0.5</span>, pcie-root and
-      dmi-to-pci-bridge <span class="since">since 1.1.2</span>,
-      pcie-root-port, pcie-switch-upstream-port,
-      pcie-switch-downstream-port <span class="since">since
-      1.2.19</span>, and pci-expander-bus and
-      pcie-expander-bus <span class="since">since 1.3.4</span>) The
-      root controllers (<code>pci-root</code>
+      PCI controllers have an optional <code>model</code> attribute; possible
+      values for this attribute are
+    </p>
+    <ul>
+      <li>
+        <code>pci-root</code>, <code>pci-bridge</code>
+        (<span class="since">since 1.0.5</span>)
+      </li>
+      <li>
+        <code>pcie-root</code>, <code>dmi-to-pci-bridge</code>
+        (<span class="since">since 1.1.2</span>)
+      </li>
+      <li>
+        <code>pcie-root-port</code>, <code>pcie-switch-upstream-port</code>,
+        <code>pcie-switch-downstream-port</code>
+        (<span class="since">since 1.2.19</span>)
+      </li>
+      <li>
+        <code>pci-expander-bus</code>, <code>pcie-expander-bus</code>
+        (<span class="since">since 1.3.4</span>)
+      </li>
+    </ul>
+    <p>
+      The root controllers (<code>pci-root</code>
       and <code>pcie-root</code>) have an
       optional <code>pcihole64</code> element specifying how big (in
       kilobytes, or in the unit specified by <code>pcihole64</code>'s