BaseTools: Remove equality operator with None

replace "== None" with "is None" and "!= None" with "is not None"

Cc: Yonghong Zhu <yonghong.zhu@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Jaben Carsey <jaben.carsey@intel.com>
Reviewed-by: Yonghong Zhu <yonghong.zhu@intel.com>

BaseTools/Source/Python/Common/ToolDefClassObject.py

@@ -53,7 +53,7 @@ class ToolDefClassObject(object):
         for Env in os.environ:
             self.MacroDictionary["ENV(%s)" % Env] = os.environ[Env]
 
-        if FileName != None:
+        if FileName is not None:
             self.LoadToolDefFile(FileName)
 
     ## LoadToolDefFile