OpaquePtr: Update polly's calls to Loads.h API

The Loads.h API changed so that a Type parameter is now mandatory in
preparation for pointer types being opaque. Unfortunately I don't build
polly routinely and it still had some uses. This just provides the
(obvious) load type in each case.

git-svn-id: https://llvm.org/svn/llvm-project/polly/trunk@365470 91177308-0d34-0410-b5e6-96231b3b80d8