r8169: use struct pcpu_sw_netstats for rx/tx packet/byte counters

Switch to the net core rx/tx byte/packet counter infrastructure.
This simplifies the code, only small drawback is some memory overhead
because we use just one queue, but allocate the counters per cpu.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>