tools: Set an initial value for indir

This variable is not documented or set up in the module. Fix this.
Signed-off-by: NSimon Glass <sjg@chromium.org>

tools/patman/tools.py

@@ -28,6 +28,9 @@ packages = {
     'lz4': 'liblz4-tool',
     }
 
+# List of paths to use when looking for an input file
+indir = []
+
 def PrepareOutputDir(dirname, preserve=False):
     """Select an output directory, ensuring it exists.