dt-bindings: dsa: sync with maintainers

The MAINTAINERS file has Andrew Lunn, Florian Fainelli, and Vladimir Oltean
listed as the maintainers for generic dsa bindings. Update dsa.yaml and
dsa-port.yaml accordingly.
Signed-off-by: Colin Foster <colin.foster@in-advantage.com>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Acked-by: Rob Herring <robh@kernel.org>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/devicetree/bindings/net/dsa/dsa-port.yaml

@@ -9,7 +9,7 @@ title: Ethernet Switch port
 maintainers:
   - Andrew Lunn <andrew@lunn.ch>
   - Florian Fainelli <f.fainelli@gmail.com>
-  - Vivien Didelot <vivien.didelot@gmail.com>
+  - Vladimir Oltean <olteanv@gmail.com>
 
 description:
   Ethernet switch port Description

Documentation/devicetree/bindings/net/dsa/dsa.yaml

@@ -9,7 +9,7 @@ title: Ethernet Switch
 maintainers:
   - Andrew Lunn <andrew@lunn.ch>
   - Florian Fainelli <f.fainelli@gmail.com>
-  - Vivien Didelot <vivien.didelot@gmail.com>
+  - Vladimir Oltean <olteanv@gmail.com>
 
 description:
   This binding represents Ethernet Switches which have a dedicated CPU