minor cleanup to SROA: when lowering type unsafe accesses to

minor cleanup to SROA: when lowering type unsafe accesses to
large integers, the first inserted value would always create
an 'or X, 0'.  Even though this is trivially zapped by
instcombine, don't bother creating this pointless instruction.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@106979 91177308-0d34-0410-b5e6-96231b3b80d8