libata: Add special ata_pio_need_iordy() handling for Compact Flash.

According to the Compact Flash specification r4.1, PIO modes 5 and 6
do not use iordy.
Signed-off-by: David Daney <ddaney@caviumnetworks.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

drivers/ata/libata-core.c

@@ -2001,6 +2001,10 @@ unsigned int ata_pio_need_iordy(const struct ata_device *adev)
 	   as the caller should know this */
 	if (adev->link->ap->flags & ATA_FLAG_NO_IORDY)
 		return 0;
+	/* CF spec. r4.1 Table 22 says no iordy on PIO5 and PIO6.  */
+	if (ata_id_is_cfa(adev->id)
+	    && (adev->pio_mode == XFER_PIO_5 || adev->pio_mode == XFER_PIO_6))
+		return 0;
 	/* PIO3 and higher it is mandatory */
 	if (adev->pio_mode > XFER_PIO_2)
 		return 1;