Revert "xhci: plat: Register shutdown for xhci_plat"

BugLink: http://bugs.launchpad.net/bugs/1765010

Pixel 2 field testers reported that when they tried to reboot their
phones with some USB devices plugged in, the reboot would get wedged and
eventually trigger watchdog reset.  Once the Pixel kernel team found a
reliable repro case, they narrowed it down to this commit's 4.4.y
backport.  Reverting the change made the issue go away.

This reverts commit b07c1251.
Signed-off-by: Greg Hackmann <ghackmann@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

drivers/usb/host/xhci-plat.c

@@ -284,7 +284,6 @@ MODULE_DEVICE_TABLE(acpi, usb_xhci_acpi_match);
 static struct platform_driver usb_xhci_driver = {
 	.probe	= xhci_plat_probe,
 	.remove	= xhci_plat_remove,
-	.shutdown	= usb_hcd_platform_shutdown,
 	.driver	= {
 		.name = "xhci-hcd",
 		.pm = DEV_PM_OPS,