USB: don't propagate FREEZE or PRETHAW suspends

This patch (as992) fixes a recently-added bug.  During a FREEZE or
PRETHAW suspend notification, non-root devices don't actually get
suspended.  So we shouldn't tell their parent hubs that they did.

(This code path used to be skipped over, until the FREEZE/PRETHAW test
got moved out of usb_suspend_both() into generic_suspend().)

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