clang/AMDGPU: Report some missing OpenCL 2.0 feature macros
Report __opencl_c_program_scope_global_variables and
__opencl_c_device_enqueue as supported. These 2.0 features are
supported but were missing from the extension map.
__opencl_c_atomic_scope_all_devices should also be reported, but
that seems to not just work by adding it to the map for some
reason.
The existing test for these macros was also broken, since it was
missing CL3.0 run lines, so add those.