net: bridge: switch to net core statistics counters handling

Use netdev->tstats instead of a member of net_bridge for storing
a pointer to the per-cpu counters. This allows us to use core
functionality for statistics handling.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Link: https://lore.kernel.org/r/9bad2be2-fd84-7c6e-912f-cee433787018@gmail.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>