[mlir][linalg] Define a depthwise 2-D convolution op

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Summary

Depends on D94548

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Not ready for review yet.

mlir/include/mlir/Dialect/Linalg/IR/LinalgNamedStructuredOpsSpec.tc

O(n, d, h, w, f) = std_addf<kd, kh, kw>(std_mulf(
     I(n, d + kd, h + kh, w + kw, c), K(f, kd, kh, kw, c)));
 }
 
 ods_def<ConvNCDHWOp>:
 def conv_3d_ncdhw(I: f32(N, C, D, H, W), K: f32(F, C, KD, KH, KW)) -> (O: f32(N, F, D, H, W)) {
   O(n, f, d, h, w) = std_addf<kd, kh, kw>(std_mulf(
     I(n, c, d + kd, h + kh, w + kw), K(f, c, kd, kh, kw)));
 }
+
+ods_def<DepthwiseConvNHWCOp>:
+def depthwise_conv_2d_nhwc(I: f32(N, IH, IW, IC), K: f32(KH, KW, IC, CM)) -> (O: f32(N, OH, OW, IC, CM))
+                      attr(strides: 2xi32)
+"""A depth-wise 2-D convolution operation.
+
+This operation performs depth-wise 2-D convolution over an input `I` and filter
+`F` and generates output `O` using the following computation:
+
+```
+O(n, oh, ow, ic, cm) = std_addf<kh, kw>(std_mulf(
+  I(n, oh * strides[0] + kh, ow * strides[1] + kw, ic), K(kh, kw, ic, cm)))
+```
+
+where
+
+* `I` is a 4-D tensor with shape `(N, IH, IW, IC)`
+* `F` is a 4-D tensor with shape `(KH, KW, IC, CM)`
+* `O` is a 5-D tensor with shape `(N, OH, OW, IC, CM)`
+
+The indexing maps for these three tensors contain 7 dimensions, following the
+order of (`N`, `OH`, `OW`, `IC`, `CM`, `KH`, `KW`).
+"""
+{
+  O(n, oh, ow, ic, cm) = std_addf<kh, kw>(std_mulf(
+    I(n, oh * strides[0] + kh, ow * strides[1] + kw, ic), K(kh, kw, ic, cm)));
+}