[OpenMP] Adjust arguments of nvptx runtime functions

[OpenMP] Adjust arguments of nvptx runtime functions

In the future the compiler will analyze whether the OpenMP
runtime needs to be (fully) initialized and avoid that overhead
if possible. The functions already take an argument to transfer
that information to the runtime, so pass in the default value 1.
(This is needed for binary compatibility with libomptarget-nvptx
currently being upstreamed.)

Differential Revision: https://reviews.llvm.org/D40354

llvm-svn: 318836