USB: don't change HC power state for a FREEZE

This patch (as1016) prevents PCI-based host controllers from
undergoing a power-state change during a FREEZE or a PRETHAW.  Such
changes are needed only during a SUSPEND.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
CC: David Brownell <david-b@pacbell.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>