tools: Set an initial value for indir

This variable is not documented or set up in the module. Fix this.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/patman/tools.py b/tools/patman/tools.py
index 1c9bf4e..bf09979 100644
--- a/tools/patman/tools.py
+++ b/tools/patman/tools.py
@@ -28,6 +28,9 @@
     '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.