This patch much improves suspend/resume behavior of EHCI, as tested with
"echo suspend > /sys/power/state" and "echo disk > /sys/power/state".

 - Quiescing the controller has to handle a case where the software has
   finished shutting down periodic and async schedules, but the hardware
   hasn't yet finished its part.

 - When suspending the root hub, be more by-the-book so that resumes
   behave better.

 - When resuming after suspend-to-disk, or in general when no port is
   suspended, the driver re-uses the initialization logic.  That logic
   needed to understand that resources don't need re-allocation, and
   that a few things need to be reset to the default state.

 - More code paths needed to notice a suspended controller, and stop
   right away.

 - To shut down the controller, start with the root hub ports and
   work up from there.

Tested by writing "suspend" or "disk" to /sys/power/state; several
systems resumed OK, at least given the associated usbcore patches.
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>