[libgomp, nvptx] Report launch dimensions in GOMP_OFFLOAD_run

[libgomp, nvptx] Report launch dimensions in GOMP_OFFLOAD_run

Using this patch, when using GOMP_DEBUG=1 and launching a kernel in
GOMP_OFFLOAD_run (used by the omp implementation), we see the kernel launch
dimensions:
...
  GOMP_OFFLOAD_run: kernel main$_omp_fn$0: \
    launch [(teams: 1), 1, 1] [(lanes: 32), (threads: 1), 1]
...

Build on x86_64-linux with nvptx accelerator, tested libgomp.

libgomp/ChangeLog:

2020-10-08  Tom de Vries  <tdevries@suse.de>

	PR libgomp/81802
	* plugin/plugin-nvptx.c (GOMP_OFFLOAD_run): Report launch
	dimensions.