[LV] Use ScalarParts for ad-hoc pointer IV scalarization (NFCI)

We can now maintain scalar values in VectorLoopValueMap. Thus, we no longer
have to create temporary vectors with insertelement instructions when handling
pointer induction variables. This case was mistakenly missed from r279649 when
refactoring the other scalarization code.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@280405 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed