kernel, manager: Track upstream changes (#195)

* These commits are carefully picked from upstream (tiann/KernelSU)

- Picked range:
8c5f485f27..e5f43a3427

Signed-off-by: Faris <rissu.ntk@gmail.com>
Co-authored-by: Wang Han <416810799@qq.com>
Co-authored-by: TwinbornPlate75 <3342733415@qq.com>
Co-authored-by: KOWX712 <leecc0503@gmail.com>
Co-authored-by: Ylarod <me@ylarod.cn>
Co-authored-by: YuKongA <70465933+YuKongA@users.noreply.github.com>
Co-authored-by: backslashxx <118538522+backslashxx@users.noreply.github.com>
Co-authored-by: 5ec1cff <56485584+5ec1cff@users.noreply.github.com>
Co-authored-by: weishu <twsxtd@gmail.com>

kernel/manager.h

@@ -40,6 +40,4 @@ static inline void ksu_invalidate_manager_uid(void)
 }
 
 int ksu_observer_init(void);
-void ksu_observer_exit(void);
-
 #endif