[ValueTracking] Remove volatile check in isGuaranteedToTransferExecutionToSuccessor

Summary: As clarified in D53184, volatile load and store do not trap. Therefore, we should remove volatile checks for instructions in  `isGuaranteedToTransferExecutionToSuccessor`.

Reviewers: jdoerfert, efriedma, nikic

Reviewed By: nikic

Subscribers: hiraditya, jfb, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D65375

llvm-svn: 367226