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

This reverts commit 4b07ce83 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: I5458aa41226201953c4c9be42e4c3993293c8b7b
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>