net: dsa: move NET_DSA_TAG_RTL4_A to right place in Kconfig/Makefile

Move things around a little so that this tag driver is alphabetically
ordered. The Kconfig file is sorted based on the tristate text.

Suggested-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Alvin Šipraga <alsi@bang-olufsen.dk>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>