selftests/bpf: Improve test coverage of bpf_mem_alloc.

bpf_obj_new() calls bpf_mem_alloc(), but doing alloc/free of 8 elements
is not triggering watermark conditions in bpf_mem_alloc.
Increase to 200 elements to make sure alloc_bulk/free_bulk is exercised.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Hou Tao <houtao1@huawei.com>
Link: https://lore.kernel.org/bpf/20230706033447.54696-12-alexei.starovoitov@gmail.com

tools/testing/selftests/bpf/progs/linked_list.c

@@ -96,7 +96,7 @@ static __always_inline
 int list_push_pop_multiple(struct bpf_spin_lock *lock, struct bpf_list_head *head, bool leave_in_map)
 {
 	struct bpf_list_node *n;
-	struct foo *f[8], *pf;
+	struct foo *f[200], *pf;
 	int i;
 
 	/* Loop following this check adds nodes 2-at-a-time in order to