commit 8a5bdaf3 never allow the runtime suspend if prepare is failed.
The complete phase is invoked when calling __device_suspend.
It allows the runtime suspend again. But if prepare is failed,
__device_suspend won't be called and the complete phase won't also
called. Thus this runtime suspend will be blocked forever.
If prepare is failed, you should allow the runtime suspend again.
Change-Id: I57c7c04609299244a042f2524e1c65dbbdd91ae3