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/Scripts/PackageDocumentTools/plugins/EdkPlugins/edk2/model/dsc.py

@@ -189,7 +189,7 @@ class DSCComponentObject(DSCSectionObject):
                 lines.append('    <%s>\n' % key)
 
                 for name, value in self._OveridePcds[key]:
-                    if value != None:
+                    if value is not None:
                         lines.append('      %s|%s\n' % (name, value))
                     else:
                         lines.append('      %s\n' % name)