BaseTools: Eot failed when enable python3

The Eot will report error when python3 enabled.
We replaced sdict with collections.OrderedDict in python3
patch set, but the sdict implement "append" method which is not
implemented in collections.OrderedDict.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Bob Feng <bob.c.feng@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>

BaseTools/Source/Python/Eot/EotMain.py

@@ -1105,7 +1105,7 @@ class MultipleFv(FirmwareVolume):
             Fv.frombuffer(Buf, 0, len(Buf))
 
             self.BasicInfo.append([Fv.Name, Fv.FileSystemGuid, Fv.Size])
-            self.FfsDict.append(Fv.FfsDict)
+            self.FfsDict.update(Fv.FfsDict)
 
 ## Class Eot
 #