[libomptarget][nvptx] Replace cuda atomic primitives with clang intrinsics

[libomptarget][nvptx] Replace cuda atomic primitives with clang intrinsics

Tested by diff of IR generated for target_impl.cu before and after. NFC. Part
of removing deviceRTL build time dependency on cuda SDK.

Reviewed By: tianshilei1992

Differential Revision: https://reviews.llvm.org/D95294