libata-acpi: Fix NULL ptr derference in ata_acpi_dev_handle

commit 6b66d958 didn't handle SATA PMP
case in ata_acpi_bind_device and will cause a NULL ptr dereference when
user attached a SATA drive to the PMP port. Fix this by checking PMP
support.

This bug is reported by Dan van der Ster in the following bugzilla page:
https://bugzilla.kernel.org/show_bug.cgi?id=48211Reported-by: NDan van der Ster <dan@vanderster.com>
Tested-by: NDan van der Ster <dan@vanderster.com>
Signed-off-by: NAaron Lu <aaron.lu@intel.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: NJeff Garzik <jgarzik@redhat.com>
Tested-by: NSimon <tangouniform@sbcglobal.net>

drivers/ata/libata-acpi.c

@@ -1105,10 +1105,15 @@ static int ata_acpi_bind_device(struct ata_port *ap, struct scsi_device *sdev,
 	struct acpi_device *acpi_dev;
 	struct acpi_device_power_state *states;
 
-	if (ap->flags & ATA_FLAG_ACPI_SATA)
-		ata_dev = &ap->link.device[sdev->channel];
-	else
+	if (ap->flags & ATA_FLAG_ACPI_SATA) {
+		if (!sata_pmp_attached(ap))
+			ata_dev = &ap->link.device[sdev->id];
+		else
+			ata_dev = &ap->pmp_link[sdev->channel].device[sdev->id];
+	}
+	else {
 		ata_dev = &ap->link.device[sdev->id];
+	}
 
 	*handle = ata_dev_acpi_handle(ata_dev);