PCI: shpchp: Make shpchp_wq non-ordered

e24dcbef ("shpchp: update workqueue usage") was described as adding
non-ordered shpchp_wq, but it actually made it an *ordered* workqueue.

This patch changes shpchp_wq to be non-ordered, as described in the
e24dcbef commit log and as was done for pciehp by a827ea30

 ("pciehp:
update workqueue usage").

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Tejun Heo <tj@kernel.org>