dt-bindings: net: dsa: add rtl8_4 and rtl8_4t tag formats

Realtek rtl8365mb DSA driver can use these two tag formats.

Cc: devicetree@vger.kernel.org
Signed-off-by: Luiz Angelo Daros de Luca <luizluca@gmail.com>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>