sched_ext: define missing cfi stubs for sched_ext

`__bpf_ops_sched_ext_ops` was missing the initialization of some struct
attributes. With

  https://lore.kernel.org/all/20240722183049.2254692-4-martin.lau@linux.dev/

every single attributes need to be initialized programs (like scx_layered)
will fail to load.

  05:26:48 [INFO] libbpf: struct_ops layered: member cgroup_init not found in kernel, skipping it as it's set to zero
  05:26:48 [INFO] libbpf: struct_ops layered: member cgroup_exit not found in kernel, skipping it as it's set to zero
  05:26:48 [INFO] libbpf: struct_ops layered: member cgroup_prep_move not found in kernel, skipping it as it's set to zero
  05:26:48 [INFO] libbpf: struct_ops layered: member cgroup_move not found in kernel, skipping it as it's set to zero
  05:26:48 [INFO] libbpf: struct_ops layered: member cgroup_cancel_move not found in kernel, skipping it as it's set to zero
  05:26:48 [INFO] libbpf: struct_ops layered: member cgroup_set_weight not found in kernel, skipping it as it's set to zero
  05:26:48 [WARN] libbpf: prog 'layered_dump': BPF program load failed: unknown error (-524)
  05:26:48 [WARN] libbpf: prog 'layered_dump': -- BEGIN PROG LOAD LOG --
  attach to unsupported member dump of struct sched_ext_ops
  processed 0 insns (limit 1000000) max_states_per_insn 0 total_states 0 peak_states 0 mark_read 0
  -- END PROG LOAD LOG --
  05:26:48 [WARN] libbpf: prog 'layered_dump': failed to load: -524
  05:26:48 [WARN] libbpf: failed to load object 'bpf_bpf'
  05:26:48 [WARN] libbpf: failed to load BPF skeleton 'bpf_bpf': -524
  Error: Failed to load BPF program

Signed-off-by: Manu Bretelle <chantr4@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

Author: chantra

kernel/sched/ext.c

@@ -5111,6 +5111,9 @@ static void cpu_online_stub(s32 cpu) {}
 static void cpu_offline_stub(s32 cpu) {}
 static s32 init_stub(void) { return -EINVAL; }
 static void exit_stub(struct scx_exit_info *info) {}
+static void dump_stub(struct scx_dump_ctx *ctx) {}
+static void dump_cpu_stub(struct scx_dump_ctx *ctx, s32 cpu, bool idle) {}
+static void dump_task_stub(struct scx_dump_ctx *ctx, struct task_struct *p) {}
 
 static struct sched_ext_ops __bpf_ops_sched_ext_ops = {
 	.select_cpu = select_cpu_stub,
@@ -5136,6 +5139,9 @@ static struct sched_ext_ops __bpf_ops_sched_ext_ops = {
 	.cpu_offline = cpu_offline_stub,
 	.init = init_stub,
 	.exit = exit_stub,
+	.dump = dump_stub,
+	.dump_cpu = dump_cpu_stub,
+	.dump_task = dump_task_stub,
 };
 
 static struct bpf_struct_ops bpf_sched_ext_ops = {