The MAC_FORCE_MODE_CTRL register is only used for the CPU port.
No need to repeat the port register calculation for each usage.
Simply point to the cpu port register directly.
Signed-off-by: Markus Stockhausen <markus.stockhausen@gmx.de>
Link: https://github.com/openwrt/openwrt/pull/22100
Signed-off-by: Robert Marko <robimarko@gmail.com>