[passes] Introduce LegalizeAvgpool2d

[dayo09]

This commit is to accept torch.nn.AvgPool2d(count_include_pad = False). count_include_pad must be true for Circle Avgpool2D. Therefore, generate mask to make equivalent operation.

TICO-DCO-1.0-Signed-off-by: Dayoung Lee dayoung.lee@samsung.com

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From #93

[mhs4670go]

I think current codes from main branch have a bit wrong assumption.

In short, just setting SAME padding option to the circle node and not creating CirclePad when the SAME padding condition is met will do the trick.

CircleAveragePool2D op has no explicit count_include_pad parameter;it just uses a fixed behavior. Circle's "SAME" padding mode for average pooling excludes the padded area from the average count. It behaves like count_include_pad=False. But, PyTorch uses count_include_pad=True by default.

Therefore, we need to explicitly introduce the padding as part of the computation so that it gets counted in the average. That is why current codes work well.

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The example module from this PR can be simply converted like this.