net: dsa: realtek: rename realtek_smi to realtek_priv

In preparation to adding other interfaces, the private data structure
was renamed to priv. Also, realtek_smi_variant and realtek_smi_ops
were renamed to realtek_variant and realtek_ops as those structs are
not SMI specific.

Signed-off-by: Luiz Angelo Daros de Luca <luizluca@gmail.com>
Tested-by: Arınç ÜNAL <arinc.unal@arinc9.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Alvin Šipraga <alsi@bang-olufsen.dk>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>