ppp: annotate concurrent dev->stats accesses

ppp: annotate concurrent dev->stats accesses

dev->stats fields can be updated concurrently from multiple CPUs
without synchronization.

Use DEV_STATS_INC() for stats increments and DEV_STATS_READ()
when reading dev->stats in ppp_get_stats64() and ppp_get_stats()
to avoid data races.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Qingfang Deng <qingfang.deng@linux.dev>
Link: https://patch.msgid.link/20260715055541.1147542-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>