net: qualcomm: rmnet: don't over-count statistics

[ Upstream commit 994c393b ]

The purpose of the loop using u64_stats_fetch_*_irq() is to ensure
statistics on a given CPU are collected atomically. If one of the
statistics values gets updated within the begin/retry window, the
loop will run again.

Currently the statistics totals are updated inside that window.
This means that if the loop ever retries, the statistics for the
CPU will be counted more than once.

Fix this by taking a snapshot of a CPU's statistics inside the
protected window, and then updating the counters with the snapshot
values after exiting the loop.

(Also add a newline at the end of this file...)

Fixes: 192c4b5d ("net: qualcomm: rmnet: Add support for 64 bit stats")
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>