[Relay][Op] Add group conv2d dispatch to topi function (apache#2870)

* [Relay][Op] Add group conv2d dispatch to topi function

* Rerun tests

python/tvm/relay/op/nn/_nn.py

@@ -96,6 +96,9 @@ def compute_conv2d(attrs, inputs, out_type, target):
          get_const_int(inputs[1].shape[3]) == 1:
         out = topi.nn.depthwise_conv2d_nhwc(
             inputs[0], inputs[1], strides, padding, dilation, out_dtype=out_dtype)
+    elif layout in ['NCHW', 'NCHW4c']:
+        out = topi.nn.group_conv2d_nchw(inputs[0], inputs[1], strides, padding, dilation, groups,
+                                        out_dtype=out_dtype)
     else:
         raise ValueError("not support arbitrary group number for now")
     return [out]
@@ -120,6 +123,8 @@ def schedule_conv2d(attrs, outs, target):
                 return topi.generic.schedule_depthwise_conv2d_nchw(outs)
             if layout == "NHWC" and kernel_layout == "HWOI":
                 return topi.generic.schedule_depthwise_conv2d_nhwc(outs)
+            if layout == "NCHW4c":
+                return topi.generic.schedule_group_conv2d_nchw(outs)
     raise ValueError("No compatible schedule")