docs: Use consistent style in pci-addresses.rst

Indent all code snippets by the same number of spaces, and don't
embed the :: marker in the line preceding a code block.

This commit is best viewed with 'git show -w'.
Signed-off-by: NAndrea Bolognani <abologna@redhat.com>
Reviewed-by: NCornelia Huck <cohuck@redhat.com>

docs/pci-addresses.rst

@@ -213,7 +213,9 @@ In the simplest case, the following XML snippet
     </address>
   </interface>
 
-will result in the following in a Linux guest::
+will result in the following in a Linux guest:
+
+::
 
   0001:00:00.0 Ethernet controller: Red Hat, Inc. Virtio network device
 
@@ -221,7 +223,7 @@ Note that the PCI bridge is not visible in the guest; s390x always has a flat
 topology.
 
 Neither are any changes in the PCI address visible in the guest; replacing
-the PCI address for the virtio-net device with
+the PCI address for the ``virtio-net`` device with
 
 ::
 
@@ -245,6 +247,8 @@ snippet
     </address>
   </interface>
 
-will yield the following result in a Linux guest::
+will yield the following result in a Linux guest:
+
+::
 
   0007:00:00.0 Ethernet controller: Red Hat, Inc. Virtio network device