iwlwifi: pcie: Refactor iwl_queue_space

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static int iwl_queue_space(const struct iwl_queue *q)

{

	int s = q->read_ptr - q->write_ptr;

	if (q->read_ptr > q->write_ptr)

		s -= q->n_bd;

	if (s <= 0)

		s += q->n_window;

	/* keep some reserve to not confuse empty and full situations */

	s -= 2;

	if (s < 0)

		s = 0;

	return s;

	unsigned int max;

	unsigned int used;

	/*

	 * To avoid ambiguity between empty and completely full queues, there

	 * should always be less than q->n_bd elements in the queue.

	 * If q->n_window is smaller than q->n_bd, there is no need to reserve

	 * any queue entries for this purpose.

	 */

	if (q->n_window < q->n_bd)

		max = q->n_window;

	else

		max = q->n_bd - 1;

	/*

	 * q->n_bd is a power of 2, so the following is equivalent to modulo by

	 * q->n_bd and is well defined for negative dividends.

	 */

	used = (q->write_ptr - q->read_ptr) & (q->n_bd - 1);

	if (WARN_ON(used > max))

		return 0;

	return max - used;

}

/*