Fix auto-upgrade for the new parameter to llvm.objectsize

r352664 added a 'dynamic' parameter to objectsize, but the AutoUpgrade
changes were incomplete. Also, fix an off-by-one error I made in the
upgrade logic that is now no longer unreachable.

Differential revision: https://reviews.llvm.org/D58071

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@353884 91177308-0d34-0410-b5e6-96231b3b80d8