libata: fix PMP initialization

libata: fix PMP initialization

Commit b81f19d55e2592d17d55176e0ae3eab766cea1b3 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>