greybus: hd: arche-platform: implement greybus shutdown

Implement platform driver shutdown callback to perform proper greybus
shutdown so that the userspace unipro_shutdown service that shuts down
the APB/SVC abruptly can be removed. The shutdown callback in
arche-platform will first remove SVC so that all the Interface can be
Deactivated in a sequence according to the spec before powering off the
APB:

Before:
 -> Arche/APB power off
 -> SoC power off

After this patch:
 -> HD shutdown
     -> SVC shutdown
         -> Module shutdown
             -> Interface shutdown
                 -> Bundle shutdown
 -> Arche/APB power off
 -> SoC power off

Testing Done:
 - Observe all Interfaces are deactivated in the log during shutdown
 - Measure power off current and make sure no regression

Signed-off-by: David Lin <dtwlin@google.com>
Reviewed-by: Vaibhav Hiremath <vaibhav.hiremath@linaro.org>
Reviewed-by: Johan Hovold <johan@hovoldconsulting.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>