bpf/tests: Use struct_size()

Use struct_size() instead of hand writing it. This is less verbose and
more informative.

Signed-off-by: Su Hui <[e-mail]>
Signed-off-by: Daniel Borkmann <[e-mail]>
Acked-by: Yonghong Song <[e-mail]>
Link: https://lore.kernel.org/bpf/[e-mail]

lib/test_bpf.c

···
 	int which, err;
 
 	/* Allocate the table of programs to be used for tall calls */
-	progs = kzalloc(sizeof(*progs) + (ntests + 1) * sizeof(progs->ptrs[0]),
-			GFP_KERNEL);
+	progs = kzalloc(struct_size(progs, ptrs, ntests + 1), GFP_KERNEL);
 	if (!progs)
 		goto out_nomem;