Fix formatting comment in Checker

Change-Id: Idf5cf2d4be12a56777039aca3aa1c8563bcb9089
diff --git a/tools/checker/file_format/checker/struct.py b/tools/checker/file_format/checker/struct.py
index 8181c4c..7ee09cd 100644
--- a/tools/checker/file_format/checker/struct.py
+++ b/tools/checker/file_format/checker/struct.py
@@ -128,12 +128,11 @@
     rVariableStartSym = r"(<<)"
     rVariableEndSym = r"(>>)"
     rVariableSeparator = r"(:)"
+    rVariableDefinitionBody = rName + rVariableSeparator + rRegex
 
     regexPattern = rPatternStartSym + rRegex + rPatternEndSym
     regexVariableReference = rVariableStartSym + rName + rVariableEndSym
-    regexVariableDefinition = (rVariableStartSym +
-                                 rName + rVariableSeparator + rRegex +
-                               rVariableEndSym)
+    regexVariableDefinition = rVariableStartSym + rVariableDefinitionBody + rVariableEndSym
 
   def __init__(self, variant, name, text):
     self.variant = variant