sched_ext: Fixes incorrect type in bpf_scx_init()

The type_id is defined as u32type, if(type_id<0) is invalid, hence
modified its type to s32.

./kernel/sched/ext.c:4958:5-12: WARNING: Unsigned expression compared with zero: type_id < 0.

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Closes: https://bugzilla.openanolis.cn/show_bug.cgi?id=9523
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

kernel/sched/ext.c

@@ -5057,7 +5057,7 @@ static void bpf_scx_unreg(void *kdata, struct bpf_link *link)
 
 static int bpf_scx_init(struct btf *btf)
 {
-	u32 type_id;
+	s32 type_id;
 
 	type_id = btf_find_by_name_kind(btf, "task_struct", BTF_KIND_STRUCT);
 	if (type_id < 0)