[Clang][OpenCL] Fix wait_for_event argument address space with -fdeclare-opencl-builtins (#134598)
The pointer argument for `wait_for_event(int, event_t*)` should take the
default address space: generic if available, otherwise private.
Before this patch it would always be generic with
`-fdeclare-opencl-builtins`. This was inconsistent with the behavior
when opencl-c.h is included.