bpf: fix u64_stats_init() usage in bpf_prog_alloc()

We need to iterate through all possible cpus.

Fixes: 492ecee8 ("bpf: enable program stats")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Guenter Roeck <linux@roeck-us.net>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>