check device list size in context

mindspore/lite/src/inner_context.cc

@@ -104,6 +104,10 @@ int InnerContext::IsValid() const {
     MS_LOG(ERROR) << "Device list is empty.";
     return RET_NOT_SUPPORT;
   }
+  if (this->device_list_.size() > 2) {
+    MS_LOG(ERROR) << "Not support device list more than 2.";
+    return RET_NOT_SUPPORT;
+  }
   if (!IsUserSetCpu()) {
     MS_LOG(ERROR) << "CPU context should be set.";
     return RET_NOT_SUPPORT;