drm/nv50/kms: use sclass() instead of trial-and-error

nv50_chan_create(struct nvif_object *disp, const u32 *oclass, u8 head,

		 void *data, u32 size, struct nv50_chan *chan)

{

	const u32 handle = (oclass[0] << 16) | head;

	u32 sclass[8];

	int ret, i;

	ret = nvif_object_sclass(disp, sclass, ARRAY_SIZE(sclass));

	WARN_ON(ret > ARRAY_SIZE(sclass));

	if (ret < 0)

		return ret;

	while (oclass[0]) {

		int ret = nvif_object_init(disp, NULL, (oclass[0] << 16) | head,

		for (i = 0; i < ARRAY_SIZE(sclass); i++) {

			if (sclass[i] == oclass[0]) {

				ret = nvif_object_init(disp, NULL, handle,

						       oclass[0], data, size,

						       &chan->user);

		if (oclass++, ret == 0) {

				if (ret == 0)

					nvif_object_map(&chan->user);

				return ret;

			}

		}

		oclass++;

	}

	return -ENOSYS;

}