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/sata_qstor.c

@@ -161,6 +161,8 @@ static const struct ata_port_operations qs_ata_ops = {
 	.eng_timeout		= qs_eng_timeout,
 	.irq_handler		= qs_intr,
 	.irq_clear		= qs_irq_clear,
+	.irq_on			= ata_irq_on,
+	.irq_ack		= ata_irq_ack,
 	.scr_read		= qs_scr_read,
 	.scr_write		= qs_scr_write,
 	.port_start		= qs_port_start,