Reapply "[OpenMP][FIX] Allow device constructors for AMD GPU"

This reverts commit a597d6a7 and
reapplies 07b17664.

In AMD GPU device code the globals are in AS(1). Before, we crashed if
the global was a structure. Now we simply cast away the AS before we
generate the code to initialize the global.

Differential Revision: https://reviews.llvm.org/D121837

Fixes: https://github.com/llvm/llvm-project/issues/54421