Revert "veth: Use tstats per-CPU traffic counters"

This reverts commit 7ca7b664 which is
commit 6f2684bf upstream.

It breaks the Android kernel abi and can be brought back in the future
in an abi-safe way if it is really needed.

Bug: 161946584
Change-Id: I77d059ea30dda952a3e58f85289a69afbca037f4
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>