Add quantized avg_pool2d for pytorch mobile (#27631)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/27631
Add support to perform avg_pool2d on mobile. Tested using existing avg_pool2d python tests
Uses qnnpack backend, which currently only support 4 dim inputs.
Test Plan:
python test/test_quantized.py TestQNNPackOps.test_avg_pool2d
Imported from OSS
Differential Revision: D17973792
fbshipit-source-id: 95ffffb2da656ed911a618b9cb68d6b728c16c74
