TX counters not updated on wireguard interface

[Jason A. Donenfeld]

Hey Baptiste,

I'll try to reproduce this shortly. I did make a change to some compat
code [1] for kernels older than 3.12 to fix a similar bug. But Jesse
has a newer kernel than that, I think? I'll check into it and try to
fix. Thanks for reporting.

Jason

[1] https://git.zx2c4.com/WireGuard/patch/?id=1370d96432c2c7e86705ce99b1682a3b7c2ce1cd