Rename options --cuda-gpu-arch and --no-cuda-gpu-arch

Per discussion

http://lists.llvm.org/pipermail/llvm-dev/2017-February/109930.html

Rename -cuda-gpu-arch and --no-cuda-gpu-arch to
--offload-arch and --no-offload-arch.

The original options will be alias to the new options.

Differential Revision: https://reviews.llvm.org/D76987