dma-buf: use struct_size macro

Instead of manually calculating the structure size.
Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/394252/

drivers/dma-buf/dma-resv.c

@@ -63,7 +63,7 @@ static struct dma_resv_list *dma_resv_list_alloc(unsigned int shared_max)
 {
 	struct dma_resv_list *list;
 
-	list = kmalloc(offsetof(typeof(*list), shared[shared_max]), GFP_KERNEL);
+	list = kmalloc(struct_size(list, shared, shared_max), GFP_KERNEL);
 	if (!list)
 		return NULL;