Deepfm -- fix the excessively high memory usage of data processing

[kaierlong]

What type of PR is this?

/kind enhancement

What does this PR do / why do we need it:
fix the excessively high memory usage of data processing for deepfm demo

Which issue(s) this PR fixes:
fix the excessively high memory usage of data processing for deepfm demo

test install and run:

git clone https://github.com/kaierlong/tinyms.git && cd tinyms
git checkout deepfm

cat requirements.txt |sed "s#mindspore#mindspore-gpu#" > requirements_gpu.txt
cat setup.py |sed "s#mindspore#mindspore-gpu#" > setup_gpu.py

pip3 install -r requirements_gpu.txt
python3 setup_gpu.py install

mkdir ~/test
cp tests/st/deepfm.py ~/test/
cd ~/test

nohup python3 deepfm.py --device_target=GPU --epoch_size=5 --batch_size=16000 --checkpoint_dir=. &

[hellowaywewe]

@kaierlong Sorry, it is so late to reply. Our team has built a new environment in recent days, I will test your code in this new environment, thanks.

[hellowaywewe]

@kaierlong Thanks for your contribution. The test has been passed, can you resolve the conflict？