Documentation: networking: dsa: demote subsections to simple emphasized words

"make htmldocs" complains:
configuration.rst:165: WARNING: duplicate label networking/dsa/configuration:single port, other instance in (...)
configuration.rst:212: WARNING: duplicate label networking/dsa/configuration:bridge, other instance in (...)
configuration.rst:252: WARNING: duplicate label networking/dsa/configuration:gateway, other instance in (...)

And for good reason, because the "single port", "bridge" and "gateway"
use cases are replicated twice, once for normal taggers and twice for
DSA_TAG_PROTO_NONE. So when trying to reference these sections via a
hyperlink such as:

https://www.kernel.org/doc/html/latest/networking/dsa/configuration.html#single-port

it will always reference the first occurrence, and never the second one.

This change makes the "single port", "bridge" and "gateway"
configuration examples consistent with the formatting used in the
"Configuration showcases" subsection.
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/networking/dsa/configuration.rst

@@ -78,10 +78,8 @@ The tagging based configuration is desired and supported by the majority of
 DSA switches. These switches are capable to tag incoming and outgoing traffic
 without using a VLAN based configuration.
 
-single port
-~~~~~~~~~~~
-
-.. code-block:: sh
+*single port*
+  .. code-block:: sh
 
     # configure each interface
     ip addr add 192.0.2.1/30 dev lan1
@@ -96,10 +94,8 @@ single port
     ip link set lan2 up
     ip link set lan3 up
 
-bridge
-~~~~~~
-
-.. code-block:: sh
+*bridge*
+  .. code-block:: sh
 
     # The master interface needs to be brought up before the slave ports.
     ip link set eth0 up
@@ -123,10 +119,8 @@ bridge
     # bring up the bridge
     ip link set dev br0 up
 
-gateway
-~~~~~~~
-
-.. code-block:: sh
+*gateway*
+  .. code-block:: sh
 
     # The master interface needs to be brought up before the slave ports.
     ip link set eth0 up
@@ -161,11 +155,10 @@ A minority of switches are not capable to use a taging protocol
 (DSA_TAG_PROTO_NONE). These switches can be configured by a VLAN based
 configuration.
 
-single port
-~~~~~~~~~~~
-The configuration can only be set up via VLAN tagging and bridge setup.
+*single port*
+  The configuration can only be set up via VLAN tagging and bridge setup.
 
-.. code-block:: sh
+  .. code-block:: sh
 
     # tag traffic on CPU port
     ip link add link eth0 name eth0.1 type vlan id 1
@@ -208,10 +201,8 @@ The configuration can only be set up via VLAN tagging and bridge setup.
     ip link set br0 up
 
 
-bridge
-~~~~~~
-
-.. code-block:: sh
+*bridge*
+  .. code-block:: sh
 
     # tag traffic on CPU port
     ip link add link eth0 name eth0.1 type vlan id 1
@@ -248,10 +239,8 @@ bridge
     # bring up the bridge
     ip link set dev br0 up
 
-gateway
-~~~~~~~
-
-.. code-block:: sh
+*gateway*
+  .. code-block:: sh
 
     # tag traffic on CPU port
     ip link add link eth0 name eth0.1 type vlan id 1