[ARM] Remove unnecessary use of replaceSymbolicStrideSCEV (NFC).

[fhahn]

Summary

When passing an empty strides map, there's nothing to replace for
replaceSymbolicStrideSCEV and it just returns the SCEV for Ptr. There
should be no need to call the function.

[SjoerdMeijer]

Yeah, sounds very reasonable to me.

llvm/lib/Target/ARM/ARMTargetTransformInfo.cpp

for (Instruction &I : BB->instructionsWithoutDebug()) {
                         "be tail-predicated\n.");
           return false;
           // TODO: don't tail predicate if there is a reversed load?
         } else if (EnableMaskedGatherScatters) {
           // Gather/scatters do allow loading from arbitrary strides, at
           // least if they are loop invariant.
           // TODO: Loop variant strides should in theory work, too, but
           // this requires further testing.
-          const SCEV *PtrScev =
-              replaceSymbolicStrideSCEV(PSE, llvm::ValueToValueMap(), Ptr);
+          const SCEV *PtrScev = PSE.getSE()->getSCEV(Ptr);
           if (auto AR = dyn_cast<SCEVAddRecExpr>(PtrScev)) {
             const SCEV *Step = AR->getStepRecurrence(*PSE.getSE());
             if (PSE.getSE()->isLoopInvariant(Step, L))
               continue;
           }
         }
         LLVM_DEBUG(dbgs() << "Bad stride found, can't "
                              "tail-predicate\n.");