Revert "AHCI: Do not acquire ata_host::lock from single IRQ handler"

This reverts commit 33fb0d01.

18dcf433 ("AHCI: Optimize single IRQ interrupt processing") is
scheduled to be reverted.  This is an optimization dependent on the
mentioned commit.  Revert it first.
Signed-off-by: NTejun Heo <tj@kernel.org>

drivers/ata/libahci.c

@@ -1875,6 +1875,8 @@ static irqreturn_t ahci_single_irq_intr(int irq, void *dev_instance)
 
 	irq_masked = irq_stat & hpriv->port_map;
 
+	spin_lock(&host->lock);
+
 	for (i = 0; i < host->n_ports; i++) {
 		struct ata_port *ap;
 
@@ -1906,6 +1908,8 @@ static irqreturn_t ahci_single_irq_intr(int irq, void *dev_instance)
 	 */
 	writel(irq_stat, mmio + HOST_IRQ_STAT);
 
+	spin_unlock(&host->lock);
+
 	VPRINTK("EXIT\n");
 
 	return handled ? IRQ_WAKE_THREAD : IRQ_NONE;