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/GenFds/OptRomFileStatement.py

@@ -41,7 +41,7 @@ class OptRomFileStatement:
     #
     def GenFfs(self, Dict = {}, IsMakefile=False):
         
-        if self.FileName != None:
+        if self.FileName is not None:
             self.FileName = GenFdsGlobalVariable.ReplaceWorkspaceMacro(self.FileName)
         
         return self.FileName