[og9] Clean up dead/write-only fields in GCN libgomp plugin

[og9] Clean up dead/write-only fields in GCN libgomp plugin

	gcc/
	* config/gcn/mkoffload.c (process_asm): Remove omp_data_size,
	gridified_kernel_p, kernel_dependencies_count, kernel_dependencies
	from emitted hsa_kernel_description struct array.

	libgomp/
	* plugin/plugin-gcn.c (GOMP_hsa_kernel_dispatch): Remove
	omp_data_memory, kernel_dispatch_count, debug, omp_level,
	children_dispatches and omp_num_threads fields.
	(hsa_kernel_description): Remove omp_data_size, gridified_kernel_p,
	kernel_dependencies_count, kernel_dependencies fields to match
	mkoffload output.
	(kernel_info): Remove omp_data_size, dependencies, dependencies_count,
	max_omp_data_size and gridified_kernel_p fields.
	(init_basic_kernel_info): Don't copy newly-deleted fields.
	(create_single_kernel_dispatch): Remove omp_data_size parameter.
	Remove write-only initialization of deleted GOMP_hsa_kernel_dispatch
	fields.
	(release_kernel_dispatch): Update debug output.  Don't free deleted
	omp_data_memory field.
	(init_single_kernel): Remove max_omp_data_size parameter. Remove deleted
	fields from debug output.
	(print_kernel_dispatch): Don't print deleted fields.
	(create_kernel_dispatch): Remove omp_data_size parameter.
	(init_kernel): Update calls to init_single_kernel and
	create_kernel_dispatch.

(cherry picked from openacc-gcc-9-branch commit
c52fb36bc65b613a718e7816682cfd4fb2e8f2b1)