docs: net: sja1105.rst: fix table format

There's a table there with produces two warnings when built
with Sphinx:

    Documentation/networking/dsa/sja1105.rst:91: WARNING: Block quote ends without a blank line; unexpected unindent.
    Documentation/networking/dsa/sja1105.rst:91: WARNING: Block quote ends without a blank line; unexpected unindent.

It will still produce a table, but the html output is wrong, as
it won't interpret the second line as the continuation for the
first ones, because identation doesn't match.

After the change, the output looks a way better and we got rid
of two warnings.
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Acked-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/networking/dsa/sja1105.rst

@@ -86,13 +86,13 @@ functionality.
 The following traffic modes are supported over the switch netdevices:
 
 +--------------------+------------+------------------+------------------+
-|                    | Standalone |   Bridged with   |   Bridged with   |
-|                    |    ports   | vlan_filtering 0 | vlan_filtering 1 |
+|                    | Standalone | Bridged with     | Bridged with     |
+|                    | ports      | vlan_filtering 0 | vlan_filtering 1 |
 +====================+============+==================+==================+
 | Regular traffic    |     Yes    |       Yes        |  No (use master) |
 +--------------------+------------+------------------+------------------+
 | Management traffic |     Yes    |       Yes        |       Yes        |
-|    (BPDU, PTP)     |            |                  |                  |
+| (BPDU, PTP)        |            |                  |                  |
 +--------------------+------------+------------------+------------------+
 
 Switching features