[og9] OpenACC profiling support for AMD GCN

[og9] OpenACC profiling support for AMD GCN

2019-09-06  Julian Brown  <julian@codesourcery.com>

	libgomp/
	* plugin/plugin-gcn.c (GOMP_OFFLOAD_alloc_by_agent,
	GOMP_OFFLOAD_free, gcn_exec): Add profiling support.
	* testsuite/libgomp.oacc-c-c++-common/acc_prof-init-1.c: Add GCN
	support.
	* testsuite/libgomp.oacc-c-c++-common/acc_prof-kernels-1.c: Likewise.
	* testsuite/libgomp.oacc-c-c++-common/acc_prof-parallel-1.c: Likewise.

(cherry picked from openacc-gcc-9-branch commit
3a62e6e8be2456f110b855386b207312478aa890)