Tlt-converter run in jetson nano with tensorrt 7.1 occured some errors

Refer to How to run tlt-converter

$ ./tlt-converter resnet18_peoplenet_pruned.etlt -k tlt_encode -c resnet18_peoplenet_int8.txt -o output_cov/Sigmoid,output_bbox/BiasAdd -d 3,544,960 -i nchw -e peoplenet_int8.engine -m 64 -t int8 -b 64