[QNN] Fix padding changes due to apache#3739 (apache#3989)

Author: anijain2305

src/relay/pass/pattern_util.h

@@ -476,10 +476,12 @@ static inline Expr AvgPool2D(Expr data, Array<IndexExpr> pool_size, Array<IndexE
   return CallNode::make(op, {data}, Attrs(attrs), {});
 }
 
-static inline Expr Pad(Expr data, Array<Array<IndexExpr>> pad_width, double pad_value) {
+static inline Expr Pad(Expr data, Array<Array<IndexExpr>> pad_width, double pad_value,
+                       std::string pad_mode) {
   auto attrs = make_node<PadAttrs>();
   attrs->pad_value = pad_value;
   attrs->pad_width = std::move(pad_width);
+  attrs->pad_mode = std::move(pad_mode);
   static const Op& op = Op::Get("nn.pad");
   return CallNode::make(op, {data}, Attrs(attrs), {});
 }

src/relay/qnn/op/convolution.cc

@@ -167,7 +167,7 @@ Expr Conv2DPadInput(const Expr& data, const QnnConv2DAttrs* param) {
     } else {
       LOG(FATAL) << "qnn.conv2d does not support " << param->data_layout << " layout";
     }
-    padded_data = Pad(data, pad_width, param->input_zero_point);
+    padded_data = Pad(data, pad_width, param->input_zero_point, "constant");
   }
   return padded_data;
 }