scsi_host regression: fix scsi host leak

scsi_host regression: fix scsi host leak

The patch is upstream as commit 3ed7897242b7efe977f3a8d06d4e5a4ebe28b10e

A different backport is necessary because of the class_device to device
conversion post 2.6.25.

commit 9c7701088a61cc0cf8a6e1c68d1e74e3cc2ee0b7
Author: Dave Young <hidave.darkstar@gmail.com>
Date:   Tue Jan 22 14:01:34 2008 +0800

    scsi: use class iteration api

Isn't a correct replacement for the original hand rolled host
lookup. The problem is that class_find_child would get a reference to
the host's class device which is never released.  Since the host class
device holds a reference to the host gendev, the host can never be
freed.

In 2.6.25 we started using class_find_device, and this function also
gets a reference to the device, so we end up with an extra ref
and the host will not get released.

This patch adds a class_put_device to balance the class_find_device()
get. I kept the scsi_host_get in scsi_host_lookup, because the target
layer is using scsi_host_lookup and it looks like it needs the SHOST_DEL
check.

Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>