bpf: Align struct bpf_prog_stats

Do not risk spanning these small structures on two cache lines.
Signed-off-by: NEric Dumazet <edumazet@google.com>
Signed-off-by: NDaniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20191011181140.2898-1-edumazet@google.com

include/linux/bpf.h

@@ -363,7 +363,7 @@ struct bpf_prog_stats {
 	u64 cnt;
 	u64 nsecs;
 	struct u64_stats_sync syncp;
-};
+} __aligned(2 * sizeof(u64));
 
 struct bpf_prog_aux {
 	atomic_t refcnt;