patman: Define Commit.path in the constructor

It is good practice to init all variables in the constructor and pylint
sometimes checks this. Fix it.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reported-by: Tom Rini <trini@konsulko.com>

tools/patman/commit.py

@@ -28,6 +28,7 @@ class Commit:
             key: rtag type (e.g. 'Reviewed-by')
             value: Set of people who gave that rtag, each a name/email string
         warn: List of warnings for this commit, each a str
+        patch (str): Filename of the patch file for this commit
     """
     def __init__(self, hash):
         self.hash = hash
@@ -40,6 +41,7 @@ class Commit:
         self.change_id = None
         self.rtags = collections.defaultdict(set)
         self.warn = []
+        self.patch = ''
 
     def __str__(self):
         return self.subject