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

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

kernel/sucompat.h

@@ -11,7 +11,7 @@ void ksu_sucompat_exit(void);
 int ksu_handle_faccessat(int *dfd, const char __user **filename_user,
 			 int *mode, int *__unused_flags);
 int ksu_handle_stat(int *dfd, const char __user **filename_user, int *flags);
-int ksu_handle_execve_sucompat(int *fd, const char __user **filename_user,
+int ksu_handle_execve_sucompat(const char __user **filename_user,
 			       void *__never_use_argv, void *__never_use_envp,
 			       int *__never_use_flags);