ahci: disable correct irq for dummy ports

irq already contains the interrupt number for the port, don't add the
port index to it.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NTejun Heo <tj@kernel.org>
Fixes: d684a90d ("ahci: per-port msix support")
Cc: stable@vger.kernel.org v4.5+

drivers/ata/libahci.c

@@ -2524,7 +2524,7 @@ static int ahci_host_activate_multi_irqs(struct ata_host *host,
 
 		/* Do not receive interrupts sent by dummy ports */
 		if (!pp) {
-			disable_irq(irq + i);
+			disable_irq(irq);
 			continue;
 		}