realtek: dsa: Drop unused traffic_get helpers

realtek: dsa: Drop unused traffic_get helpers

The realtek driver is now in full control of the port matrix. It doesn't
need to rely on the current state of the HW to adjust it. The new port
matrix is calculated automatically using rtldsa_update_port_member() and
then written to the registers/tables.

Signed-off-by: Sven Eckelmann <se@simonwunderlich.de>
Link: https://github.com/openwrt/openwrt/pull/20360
Signed-off-by: Robert Marko <robimarko@gmail.com>