BaseTools: Remove unused logic for EDKI

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=1350
Remove gEcpSource global variable in python tool.

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

BaseTools/Source/Python/Workspace/DscBuildData.py

@@ -709,7 +709,6 @@ class DscBuildData(PlatformBuildClassObject):
     def OverrideDuplicateModule(self):
         RecordList = self._RawData[MODEL_META_DATA_COMPONENT, self._Arch]
         Macros = self._Macros
-        Macros["EDK_SOURCE"] = GlobalData.gEcpSource
         Components = {}
         for Record in RecordList:
             ModuleId = Record[6]