USB: Add new PM callback methods for USB

This patch (as1129) adds support for the new PM callbacks to usbcore.
The new callbacks merely invoke the same old USB power management
routines as the old ones did.

A minor improvement is that the callbacks are present only in the
"USB-device" device_type structure, rather than in the bus_type
structure.  This way they will be invoked only for USB devices, not
for USB interfaces.  The core USB PM routines automatically handle
suspending and resuming interfaces along with their devices.

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