realtek: dsa: remove half-cooked SoC version determination

realtek: dsa: remove half-cooked SoC version determination

There are some code pieces that determine the SoC version of the
running system. For RTL83xx it reads out the registers, for RTL93xx
it simply uses a constant value. Without any consumer of this data
drop it.

Signed-off-by: Markus Stockhausen <markus.stockhausen@gmx.de>
Link: https://github.com/openwrt/openwrt/pull/21684
Signed-off-by: Robert Marko <robimarko@gmail.com>