USB: EHCI: use hrtimer for controller death

This patch (as1578) adds an hrtimer event to handle the death of an
EHCI controller.  When a controller dies, it doesn't necessarily stop
running right away.  The new event polls at 1-ms intervals to see when
all activity has safely stopped.  This replaces a busy-wait polling
loop in the current code.

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