scripts: Move path helper into common_codegen.py

Change-Id: I0b66a8d42aa8a6ab5205d496de3df8fc253e2a54
diff --git a/scripts/common_codegen.py b/scripts/common_codegen.py
index 4adb329..a3d95e7 100644
--- a/scripts/common_codegen.py
+++ b/scripts/common_codegen.py
@@ -20,7 +20,6 @@
 
 import os,re,sys,string
 import xml.etree.ElementTree as etree
-from generator import *
 from collections import namedtuple, OrderedDict
 
 # Copyright text prefixing all headers (list of strings).
@@ -106,3 +105,8 @@
     outdent = re.sub(fake_indent, indent, string_out)
     return outdent[1:]
 
+
+# helper to define paths relative to the repo root
+def repo_relative(path):
+    return os.path.abspath(os.path.join(os.path.dirname(__file__), '..', path))
+