Downloading float model from model zoo - 2.5 English

Take tensorflow resnet50 for example.

[Host]$ cd Vitis-AI
[Host]$ wget https://www.xilinx.com/bin/public/openDownload?filename=tf_resnetv1_50_imagenet_224_224_6.97G_2.5.zip -O tf_resnetv1_50_imagenet_224_224_6.97G_2.5.zip
[Host]$ unzip tf_resnetv1_50_imagenet_224_224_6.97G_2.5.zip