dma-buf: allow reserving more than one shared fence slot

Let's support simultaneous submissions to multiple engines.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Michel Dänzer <michel.daenzer@amd.com>
Reviewed-by: Junwei Zhang <Jerry.Zhang@amd.com>
Reviewed-by: Huang Rui <ray.huang@amd.com>
Link: https://patchwork.kernel.org/patch/10626149/

drivers/gpu/drm/vc4/vc4_gem.c

@@ -635,7 +635,7 @@ retry:
 	for (i = 0; i < exec->bo_count; i++) {
 		bo = to_vc4_bo(&exec->bo[i]->base);
 
-		ret = reservation_object_reserve_shared(bo->resv);
+		ret = reservation_object_reserve_shared(bo->resv, 1);
 		if (ret) {
 			vc4_unlock_bo_reservations(dev, exec, acquire_ctx);
 			return ret;