[Clang][OpenMP] Update driver test case for OpenMP offload to use sm_35

`sm_35` is the minimum requirement for OpenMP offloading on NVPTX device.
Current driver test case is using `sm_20`. D97003 is going to switch the minimum
CUDA version to 9.2, which only supports `sm_30+`. This patch makes step for the
change.

Reviewed By: JonChesterfield

Differential Revision: https://reviews.llvm.org/D97120