Fix: srcrev bump 4b258ac8b6..7883f58ab2

Add missed python variable initialization causing srcrev bump fail

Failed srcrev bump:
    https://gerrit.openbmc-project.xyz/18414

Change-Id: I0d7d4647abe3c2f46cabfebf6be5ab500641f504
Signed-off-by: Matthew Barth <msbarth@us.ibm.com>
diff --git a/control/gen-fan-zone-defs.py b/control/gen-fan-zone-defs.py
index 7db3d95..e875e32 100755
--- a/control/gen-fan-zone-defs.py
+++ b/control/gen-fan-zone-defs.py
@@ -810,6 +810,7 @@
                 profiles = z['cooling_profiles']
 
             # 'interfaces' is optional (no default)
+            ifaces = []
             if ('interfaces' in z) and \
                     (z['interfaces'] is not None):
                 ifaces = getIfacesInZone(z['interfaces'])