netfilter: add missing xt_log.h file

#define S_SIZE (1024 - (sizeof(unsigned int) + 1))

struct sbuff {

	unsigned int	count;

	char		buf[S_SIZE + 1];

};

static struct sbuff emergency, *emergency_ptr = &emergency;

static int sb_add(struct sbuff *m, const char *f, ...)

{

	va_list args;

	int len;

	if (likely(m->count < S_SIZE)) {

		va_start(args, f);

		len = vsnprintf(m->buf + m->count, S_SIZE - m->count, f, args);

		va_end(args);

		if (likely(m->count + len < S_SIZE)) {

			m->count += len;

			return 0;

		}

	}

	m->count = S_SIZE;

	printk_once(KERN_ERR KBUILD_MODNAME " please increase S_SIZE\n");

	return -1;

}

static struct sbuff *sb_open(void)

{

	struct sbuff *m = kmalloc(sizeof(*m), GFP_ATOMIC);

	if (unlikely(!m)) {

		local_bh_disable();

		do {

			m = xchg(&emergency_ptr, NULL);

		} while (!m);

	}

	m->count = 0;

	return m;

}

static void sb_close(struct sbuff *m)

{

	m->buf[m->count] = 0;

	printk("%s\n", m->buf);

	if (likely(m != &emergency))

		kfree(m);

	else {

		xchg(&emergency_ptr, m);

		local_bh_enable();

	}

}