libata: -ENODEV during prereset isn't an error

During prereset, -ENODEV return from ata_wait_ready() is not an error.
This causes unnecessary bug message on controllers which uses 0xff to
indicate empty port. Fix it.

Signed-off-by: Tejun Heo <[e-mail]>
Cc: Paul Mundt <[e-mail]>
Signed-off-by: Jeff Garzik <[e-mail]>

drivers/ata/libata-core.c

···
 	 */
 	if (!(ap->flags & ATA_FLAG_SKIP_D2H_BSY) && !ata_port_offline(ap)) {
 		rc = ata_wait_ready(ap, deadline);
-		if (rc) {
+		if (rc && rc != -ENODEV) {
 			ata_port_printk(ap, KERN_WARNING, "device not ready "
 					"(errno=%d), forcing hardreset\n", rc);
 			ehc->i.action |= ATA_EH_HARDRESET;