net: remove comments on struct rtnl_link_stats

We removed the misleading comments from struct rtnl_link_stats64
when we added proper kdoc. struct rtnl_link_stats has the same
inline comments, so remove them, too.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: Saeed Mahameed <saeedm@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>