USB: add usbfs stubs for suspend and resume

This patch (as1022b) adds stub methods for suspend and resume to the
usbfs driver.  There isn't much they can do since there's no way to
inform a user task about the events.  But it's important to have the
stubs, because an upcoming change to usbcore will automatically unbind
drivers that don't have those methods when a suspend occurs.

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