Make prepareModel asynchronous.

Updated the corresponding VTS tests.

Bug: 63905942
Test: mm, vts
Change-Id: Ie520af845f491dbdd93ea66fd643d77cfb4703f7
diff --git a/neuralnetworks/1.0/IDevice.hal b/neuralnetworks/1.0/IDevice.hal
index b826b23..9e19097 100644
--- a/neuralnetworks/1.0/IDevice.hal
+++ b/neuralnetworks/1.0/IDevice.hal
@@ -18,6 +18,7 @@
 
 package android.hardware.neuralnetworks@1.0;
 
+import IEvent;
 import IPreparedModel;
 
 interface IDevice {
@@ -25,7 +26,7 @@
 
     getSupportedSubgraph(Model model) generates(vec<bool> supported);
 
-    prepareModel(Model model) generates(IPreparedModel preparedModel);
+    prepareModel(Model model, IEvent event) generates(IPreparedModel preparedModel);
 
     getStatus() generates(DeviceStatus status);
 };