Revert "can: statistics: use atomic access in hot path"

This reverts commit 9d257888 which is
commit 80b5f901 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: I90f0281d9af75348e0491947d77774192f22fd1a
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>