[OpenMP][OMPT] Fix locking testcases for 32 bit architectures

https://reviews.llvm.org/D58454 did not fix the problem for a typical use
case of building LLVM with gcc or icc and then testing with the newly built
clang compiler.
The compilers do not agree on how to extend a 32-bit pointer to uint64, so
make the pointer unsigned first, before adjusting the size.

Patch by Joachim Protze

Differential Revision: https://reviews.llvm.org/D58506

git-svn-id: https://llvm.org/svn/llvm-project/openmp/trunk@361158 91177308-0d34-0410-b5e6-96231b3b80d8