cpu-o3: disable abtb using s3 pred update to fix perf issue

Change-Id: Id5f8b676fb97abf35990389db1a1dfd1ccd0049a

Author: Yakkhini

src/cpu/pred/BranchPredictor.py

@@ -1000,7 +1000,7 @@ class AheadBTB(TimedBaseBTBPredictor):
     entryHalfAligned = Param.Bool(False, "Whether the entries are half-aligned")
     blockSize = 64
     numDelay = 0
-    usingS3Pred = Param.Bool(True, "Whether using S3 predictor to update AheadBTB")
+    usingS3Pred = Param.Bool(False, "Whether using S3 predictor to update AheadBTB")
 
 class UBTB(TimedBaseBTBPredictor):
     type = 'UBTB'