libata: add another IRQ calls (libata drivers)

This patch is against each libata driver.

Two IRQ calls are added in ata_port_operations.
- irq_on() is used to enable interrupts.
- irq_ack() is used to acknowledge a device interrupt.

In most drivers, ata_irq_on() and ata_irq_ack() are used for
irq_on and irq_ack respectively.

In some drivers (ex: ahci, sata_sil24) which cannot use them
as is, ata_dummy_irq_on() and ata_dummy_irq_ack() are used.

Signed-off-by: Kou Ishizaki <kou.ishizaki@toshiba.co.jp>
Signed-off-by: Akira Iguchi <akira2.iguchi@toshiba.co.jp>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

drivers/ata/ahci.c

@@ -260,6 +260,8 @@ static const struct ata_port_operations ahci_ops = {
 
 	.irq_handler		= ahci_interrupt,
 	.irq_clear		= ahci_irq_clear,
+	.irq_on			= ata_dummy_irq_on,
+	.irq_ack		= ata_dummy_irq_ack,
 
 	.scr_read		= ahci_scr_read,
 	.scr_write		= ahci_scr_write,
@@ -291,6 +293,8 @@ static const struct ata_port_operations ahci_vt8251_ops = {
 
 	.irq_handler		= ahci_interrupt,
 	.irq_clear		= ahci_irq_clear,
+	.irq_on			= ata_dummy_irq_on,
+	.irq_ack		= ata_dummy_irq_ack,
 
 	.scr_read		= ahci_scr_read,
 	.scr_write		= ahci_scr_write,