[PATCH] libata: fix ata_device_add() error path

In the error path, ata_device_add()

* dereferences null host_set->ports[] element.
* calls scsi_remove_host() on not-yet-added shost.

This patch fixes both bugs.  The first problem was spotted and initial
patch submitted by Dave Jones <davej@redhat.com>.  The second problem
was mentioned and fixed by Jeff Garzik <jgarzik@pobox.com> in a larger
cleanup patch.

Cc: Dave Jones <davej@redhat.com>
Cc: Jeff Garzik <jgarzik@pobox.com>
Signed-off-by: Tejun Heo <htejun@gmail.com>

drivers/scsi/libata-core.c

@@ -5511,10 +5511,10 @@ int ata_device_add(const struct ata_probe_ent *ent)
 err_out:
 	for (i = 0; i < count; i++) {
 		struct ata_port *ap = host_set->ports[i];
-
-		scsi_remove_host(ap->host);
-		ap->ops->port_stop(ap);
-		scsi_host_put(ap->host);
+		if (ap) {
+			ap->ops->port_stop(ap);
+			scsi_host_put(ap->host);
+		}
 	}
 err_free_ret:
 	kfree(host_set);