qconfig: Fix pylint error in read_database()

Fix this error by initing the variable before the loop:

tools/qconfig.py:880:22: E0606: Possibly using variable 'defconfig'
   before assignment (possibly-used-before-assignment)

Signed-off-by: Simon Glass <sjg@chromium.org>

diff --git a/tools/qconfig.py b/tools/qconfig.py
index 04118d9..2492b37 100755 (executable)
--- a/tools/qconfig.py
+++ b/tools/qconfig.py
@@ -873,6 +873,7 @@ def read_database():
     all_defconfigs = set()
 
     defconfig_db = collections.defaultdict(set)
+    defconfig = None
     for line in read_file(CONFIG_DATABASE):
         line = line.rstrip()
         if not line:  # Separator between defconfigs