[opaque pointer type] Remove some backwards compatible GEP APIs

Just doing the two-step so I don't get so much build-bot spam... (add
new API, migrate callers, remove old API)

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@234132 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed