Correct Tensor order for dilation2D

[gabriel-vanzandycke]

gen_nn_ops.dilation2d seems to be in NHWC while the parent function was asking for NCHW.
I corrected the doc and the check.

RELNOTES: tf.nn.dilation2d now correctly requires its data_format argument to be "NHWC".

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[gabriel-vanzandycke]

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[sjamesr]

Thank you for the change, I think it's correct but let me follow up with more knowledgeable folks in the TF team before I approve it.

[martinwicke]

This change is correct. Bummer.

[martinwicke]

@gabriel-vanzandycke can you also correct the converter tool to add the data_format arg? It should be parallel to the entry for erosion2d: https://github.com/tensorflow/tensorflow/blob/master/tensorflow/tools/compatibility/tf_upgrade_v2.py#L1525

@tomerk The converter didn't do the right thing here, can you review the change to make sure it will once @gabriel-vanzandycke is done?

@tensorflow/api-owners This is a bug affecting the API: the accepted string has changed. The old state is a bug, we need to fix it. I added relnotes.

[martinwicke]

Please add the converter code, see other comment.

[martinwicke]

Let's get this in, I'll submit the converter change separately.