CodeGen: replace use of @llvm.arm.sevl with @llvm.arm.hint

Use the new generic @llvm.arm.hint hint intrinsic rather than the specialised
@llvm.arm.sevl hint instruction.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@207243 91177308-0d34-0410-b5e6-96231b3b80d8