[orf] Fix typo

youtube_dl/extractor/orf.py

@@ -160,7 +160,7 @@ class ORFOE1IE(InfoExtractor):
 
 
 class ORFFM4IE(InfoExtractor):
-    IE_DESC = 'orf:fm4'
+    IE_NAME = 'orf:fm4'
     IE_DESC = 'radio FM4'
     _VALID_URL = r'http://fm4\.orf\.at/7tage/?#(?P<date>[0-9]+)/(?P<show>\w+)'