[libata] mark certain hardware (or drivers) with a no-atapi flag

Some hardware does not support the PACKET command at all.
Other hardware supports ATAPI, but the driver does something nasty such
as calling BUG() when an ATAPI command is issued.

For these such cases, we mark them with a new flag, ATA_FLAG_NO_ATAPI.

Initial version contributed by Ben Collins.
diff --git a/drivers/scsi/libata-scsi.c b/drivers/scsi/libata-scsi.c
index 379e870..72ddba9 100644
--- a/drivers/scsi/libata-scsi.c
+++ b/drivers/scsi/libata-scsi.c
@@ -2173,9 +2173,12 @@
 	if (unlikely(!ata_dev_present(dev)))
 		return NULL;
 
-	if (!atapi_enabled) {
-		if (unlikely(dev->class == ATA_DEV_ATAPI))
+	if (!atapi_enabled || (ap->flags & ATA_FLAG_NO_ATAPI)) {
+		if (unlikely(dev->class == ATA_DEV_ATAPI)) {
+			printk(KERN_WARNING "ata%u(%u): WARNING: ATAPI is %s, device ignored.\n",
+			       ap->id, dev->devno, atapi_enabled ? "not supported with this driver" : "disabled");
 			return NULL;
+		}
 	}
 
 	return dev;