Add mkldnn support for adaptive_avg_pool2d (#19818)
Summary:
AdaptiveAvgPool2d is used in torchvision resnet models https://github.com/pytorch/vision/blob/9a481d0/torchvision/models/resnet.py#L145
Fixes #19797
Pull Request resolved: https://github.com/pytorch/pytorch/pull/19818
Differential Revision: D15112777
Pulled By: bddppq
fbshipit-source-id: 6c9b29c805d28356cda49c10c2cd3ce9d7a8b3f5
