Merge branch 'u64_stats_t'

Eric Dumazet says:

====================
net: introduce u64_stats_t

KCSAN found a data-race in per-cpu u64 stats accounting.

(The stack traces are included in the 8th patch :
 tun: switch to u64_stats_t)

This patch series first consolidate code in five patches.
Then the last three patches address the data-race resolution.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>