customize the onnx namespace (#526)

Co-authored-by: Paul Fultz II <pfultz2@yahoo.com>

src/onnx/onnx.cpp

@@ -21,6 +21,8 @@
 namespace migraphx {
 inline namespace MIGRAPHX_INLINE_NS {
 
+namespace onnx = onnx_for_migraphx;
+
 struct onnx_parser
 {
     using attribute_map = std::unordered_map<std::string, onnx::AttributeProto>;

src/onnx/onnx.proto

@@ -8,7 +8,7 @@
 
 syntax = "proto2";
 
-package onnx;
+package onnx_for_migraphx;
 
 // Overview
 //