binman: Move the comment for GetFdts() to the base class

Like with other methods this comment should be in the base class. Move it.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/binman/entry.py b/tools/binman/entry.py
index 507760e..be94195 100644
--- a/tools/binman/entry.py
+++ b/tools/binman/entry.py
@@ -205,7 +205,7 @@
             Dict:
                 key: Filename from this entry (without the path)
                 value: Tuple:
-                    Fdt object for this dtb, or None if not available
+                    Entry object for this dtb
                     Filename of file containing this dtb
         """
         return {}
diff --git a/tools/binman/etype/blob_dtb.py b/tools/binman/etype/blob_dtb.py
index 724647a..3ce7511 100644
--- a/tools/binman/etype/blob_dtb.py
+++ b/tools/binman/etype/blob_dtb.py
@@ -44,15 +44,6 @@
         return None
 
     def GetFdts(self):
-        """Get the device trees used by this entry
-
-        Returns:
-            Dict:
-                key: Filename from this entry (without the path)
-                value: Tuple:
-                    Fdt object for this dtb, or None if not available
-                    Filename of file containing this dtb
-        """
         fname = self.GetDefaultFilename()
         return {self.GetFdtEtype(): [self, fname]}