update quantization
Signed-off-by: slyned <slyned@nvidia.com>

Add CER support

But the results of speech_to_text_quant_infer_trt.py and speech_to_text_quant_infer.py are a little different.

I've also tried to use speech_to_text_quant_infer_trt.py to do inference with NeMo models downloaded from ngc without adding --qat,  but the results also are not consistent with speech_to_text_infer.py.

