fix depthwise conv (#29227)

python/paddle/nn/layer/conv.py

@@ -143,9 +143,10 @@ class _ConvNd(layers.Layer):
                                    cudnn_version is not None) else False
 
         self._op_type = "conv" + str(dims) + 'd'
-        if dims == 2 and (in_channels == groups and in_channels != 1 and
-                          out_channels % in_channels == 0):
-            self.op_type = 'depthwise_conv2d'
+        if self._op_type == 'conv2d' and (in_channels == groups and
+                                          in_channels != 1 and
+                                          out_channels % in_channels == 0):
+            self._op_type = 'depthwise_conv2d'
             self._use_cudnn = False