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

This reverts commit 051be169 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: I873517fe5d50d622c828996ab64b2aedab7882f4
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>