Fix initialization of HW acceleration (#3209)

Summary:
Pull Request resolved: https://github.com/pytorch/audio/pull/3209

The previous code prints out the uninitialized variable when
invalid HW acceleration is provided.

This commit fixes it.

Reviewed By: hwangjeff

Differential Revision: D44449715

fbshipit-source-id: 8b76cfc27816d5ea9fbc2bc37a3148f09a8ed6ed

torchaudio/csrc/ffmpeg/stream_reader/stream_reader.cpp

@@ -306,9 +306,7 @@ void StreamReader::add_video_stream(
 #ifdef USE_CUDA
     torch::Device d{hw_accel.value()};
     TORCH_CHECK(
-        d.type() == c10::DeviceType::CUDA,
-        "Only CUDA is supported for hardware acceleration. Found: ",
-        device.str());
+        d.is_cuda(), "Only CUDA is supported for HW acceleration. Found: ", d);
     return d;
 #else
     TORCH_CHECK(