libata: fix PMP initialization

Commit 842faa6c1a1d6faddf3377948e5cf214812c6c90 fixed error handling
during attach by not committing detected device class to dev->class
while attaching a new device.  However, this change missed the PMP
class check in the configuration loop causing a new PMP device to go
through ata_dev_configure() as if it were an ATA or ATAPI device.

As PMP device doesn't have a regular IDENTIFY data, this makes
ata_dev_configure() tries to configure a PMP device using an invalid
data.  For the most part, it wasn't too harmful and went unnoticed but
this ends up clearing dev->flags which may have ATA_DFLAG_AN set by
sata_pmp_attach().  This means that SATA_PMP_FEAT_NOTIFY ends up being
disabled on PMPs and on PMPs which honor the flag breaks hotplug
support.

This problem was discovered and reported by Ethan Hsiao.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Ethan Hsiao <ethanhsiao@jmicron.com>
Cc: stable@kernel.org
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

drivers/ata/libata-eh.c

@@ -2981,12 +2981,14 @@ static int ata_eh_revalidate_and_attach(struct ata_link *link,
 	 * device detection messages backwards.
 	 */
 	ata_for_each_dev(dev, link, ALL) {
-		if (!(new_mask & (1 << dev->devno)) ||
-		    dev->class == ATA_DEV_PMP)
+		if (!(new_mask & (1 << dev->devno)))
 			continue;
 
 		dev->class = ehc->classes[dev->devno];
 
+		if (dev->class == ATA_DEV_PMP)
+			continue;
+
 		ehc->i.flags |= ATA_EHI_PRINTINFO;
 		rc = ata_dev_configure(dev);
 		ehc->i.flags &= ~ATA_EHI_PRINTINFO;