Clean up kernel code (#2898)

1) Fix memory leak of callback head in allowlist.c
2) Remove duplicated logic and incorrect log in kernel_umount.c
3) Prevent sleep in kprobe context in ksud.c
4) Remove useless is_unsupported_uid, use euid for security enhance,
   add FIXME in setuid_hook.c
5) Remove useless fd argument for execve hook, fix incorrent pointer
   usage in syscall_hook_manager.c and sucompat.c
6) Use correct errno in supercalls.c

---------

Co-authored-by: Ylarod <me@ylarod.cn>

kernel/ksud.c

@@ -209,7 +209,6 @@ static int __maybe_unused count(struct user_arg_ptr argv, int max)
 
             if (fatal_signal_pending(current))
                 return -ERESTARTNOHAND;
-            cond_resched();
         }
     }
     return i;