If ohci-platform is runtime suspended, we can currently get an "imprecise
external abort" on reboot with ohci-platform loaded when PM runtime
is implemented for the SoC.

Let's fix this by adding PM runtime support to usb_hcd_platform_shutdown.
Signed-off-by: Tony Lindgren <tony@atomide.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>