trouble with dedicating multiple GPU speech_to_text_bpe
Hi, I've trouble with dedicating multiple GPU for asr/speech_to_text_bpe.py.
In config file of conformer, I tried gpu=-1 and also gpu=2 but when I run the code, it just use the first GPU and it doesn't use the second one.
Could you please help me to solve it?
As you see when I run the code, it use just the first GPU and just use 11Mb of the second one.

![Screenshot from 2021-12-08 16-58-13](https://user-images.githubusercontent.com/95332871/145216745-c1413158-3836-489b-a3c6-58f32df45470.png)
