plugin-nvptx.c (struct targ_fn_descriptor): Move later.

plugin-nvptx.c (struct targ_fn_descriptor): Move later.

	* plugin/plugin-nvptx.c (struct targ_fn_descriptor): Move later.
	(struct ptx_image_data): Move earlier, add fns field.
	(struct ptx_device): Add images and image_lock fields.
	(ptx_images, ptx_image_lock): Delete.
	(nvptx_open_device): Initialize images and image_lock fields.
	(nvptx_close_device): Destroy image_lock.
	(GOMP_OFFLOAD_load_image): Register image to device-specific fields.
	(GOMP_OFFLOAD_unload_image): Unregister image from device-specific
	fields.

From-SVN: r226004