Revert "nvme-pci: Make driver prefer asynchronous shutdown"

This reverts commit ba82e10c.

The series is being reverted before -rc1 as there are still reports of
lockups on shutdown, so it's not quite ready for "prime time."
Reported-by: Andrey Skvortsov <andrej.skvortzov@gmail.com>
Link: https://lore.kernel.org/r/ZvMkkhyJrohaajuk@skv.local
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Jeffery <djeffery@redhat.com>
Cc: Keith Busch <kbusch@kernel.org>
Cc: Laurence Oberman <loberman@redhat.com>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Sagi Grimberg <sagi@grimberg.me>
Cc: Stuart Hayes <stuart.w.hayes@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/nvme/host/pci.c

@@ -3580,7 +3580,6 @@ static struct pci_driver nvme_driver = {
 	.shutdown	= nvme_shutdown,
 	.driver		= {
 		.probe_type	= PROBE_PREFER_ASYNCHRONOUS,
-		.async_shutdown_enable	= true,
 #ifdef CONFIG_PM_SLEEP
 		.pm		= &nvme_dev_pm_ops,
 #endif