dt-bindings: net: dsa: Extend switch nodes pattern

Upon discussion with Kurt, Rob and Vladimir it appears that we should be
allowing ethernet-switch as a node name, update dsa.yaml accordingly.

Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>