This patch (as1331) adds non-tree ordering constraints needed for
proper resume of PCI USB host controllers from hibernation.  The main
issue is that non-high-speed devices must not be resumed before the
high-speed root hub, because it is the ehci_bus_resume() routine which
takes care of handing the device connection over to the companion
controller.  If the device resume is attempted before the handover
then the device won't be found and it will be treated as though it had
disconnected.

The patch adds a new field to the usb_bus structure; for each
full/low-speed bus this field will contain a pointer to the companion
high-speed bus (if one exists).  It is used during normal device
resume; if the hs_companion pointer isn't NULL then we wait for the
root-hub device on the hs_companion bus.

A secondary issue is that an EHCI controlller shouldn't be resumed
before any of its companions.  On some machines I have observed
handovers failing if the companion controller is reinitialized after
the handover.  Thus, the EHCI resume routine must wait for the
companion controllers to be resumed.

The patch also fixes a small bug in usb_hcd_pci_probe(); an error path
jumps to the wrong label, causing a memory leak.

[rjw: Fixed compilation for CONFIG_PM_SLEEP unset.]
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Acked-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>