[DEBUG_INFO][NVPTX] Generate correct data about variable address class.

[DEBUG_INFO][NVPTX] Generate correct data about variable address class.

Summary:
Added ability to generate correct debug info data about the variable
address class. Currently, for all the locals and globals the default
values are used, ADDR_local_space(6) for locals and ADDR_global_space(5)
for globals. The values are taken from the table in
  https://docs.nvidia.com/cuda/archive/10.0/ptx-writers-guide-to-interoperability/index.html#cuda-specific-dwarf.
  We need to emit correct data for address classes of, at least, shared
  and constant globals. Currently, all these variables are treated by
  the cuda-gdb debugger as the variables in the global address space
  and, thus, it require manual data type casting.

Reviewers: echristo, probinson

Subscribers: jholewinski, aprantl, cfe-commits

Differential Revision: https://reviews.llvm.org/D57162

llvm-svn: 353204