[llvm] Remove uses of Type::getPointerTo() (NFC)

* Remove if its sole use is to support an unnecessary ptr-to-ptr bitcast
  (remove the bitcast as well)
* Replace with use of other APIs.

NFC opaque pointer cleanup effort.

GitOrigin-RevId: 4346aaf05b66a204a7c21fad8e7673860e0270eb
6 files changed