Rename Pad operator to Constant Pad in Operator API

PiperOrigin-RevId: 312838474
diff --git a/src/xnnpack/operator.h b/src/xnnpack/operator.h
index e32a4b6..1cfc3b1 100644
--- a/src/xnnpack/operator.h
+++ b/src/xnnpack/operator.h
@@ -57,6 +57,7 @@
   xnn_operator_type_channel_shuffle_nc_x8,
   xnn_operator_type_clamp_nc_f32,
   xnn_operator_type_clamp_nc_u8,
+  xnn_operator_type_constant_pad_nd_x32,
   xnn_operator_type_convolution_nhwc_f32,
   xnn_operator_type_convolution_nhwc_q8,
   xnn_operator_type_convolution_nchw_f32,
@@ -75,7 +76,6 @@
   xnn_operator_type_maximum_nd_f32,
   xnn_operator_type_minimum_nd_f32,
   xnn_operator_type_multiply_nd_f32,
-  xnn_operator_type_pad_nd_x32,
   xnn_operator_type_prelu_nc_f32,
   xnn_operator_type_resize_bilinear_nhwc_f32,
   xnn_operator_type_sigmoid_nc_f32,