usbcore: small changes to hub driver's suspend method

This patch (as847) makes some small changes to the hub driver's
suspend method:

	For root hubs, the status URB should be unlinked and other
	activity stopped _before_ the bus_suspend method is called.

	The test for hdev->bus being NULL has been removed, since
	it can never succeed.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>