dmar: use spin_lock_irqsave() in qi_submit_sync()

	hw = qi->desc;

	spin_lock(&qi->q_lock);

	spin_lock_irqsave(&qi->q_lock, flags);

	while (qi->free_cnt < 3) {

		spin_unlock(&qi->q_lock);

		spin_unlock_irqrestore(&qi->q_lock, flags);

		cpu_relax();

		spin_lock(&qi->q_lock);

		spin_lock_irqsave(&qi->q_lock, flags);

	}

	index = qi->free_head;

	qi->free_head = (qi->free_head + 2) % QI_LENGTH;

	qi->free_cnt -= 2;

	spin_lock_irqsave(&iommu->register_lock, flags);

	spin_lock(&iommu->register_lock);

	/*

	 * update the HW tail register indicating the presence of

	 * new descriptors.

	 */

	writel(qi->free_head << 4, iommu->reg + DMAR_IQT_REG);

	spin_unlock_irqrestore(&iommu->register_lock, flags);

	spin_unlock(&iommu->register_lock);

	while (qi->desc_status[wait_index] != QI_DONE) {

		/*

		 * We will leave the interrupts disabled, to prevent interrupt

		 * context to queue another cmd while a cmd is already submitted

		 * and waiting for completion on this cpu. This is to avoid

		 * a deadlock where the interrupt context can wait indefinitely

		 * for free slots in the queue.

		 */

		spin_unlock(&qi->q_lock);

		cpu_relax();

		spin_lock(&qi->q_lock);

	qi->desc_status[index] = QI_DONE;

	reclaim_free_desc(qi);

	spin_unlock(&qi->q_lock);

	spin_unlock_irqrestore(&qi->q_lock, flags);

}

/*