binder: fix memory leak in binder_init()

In the Linux kernel, the following vulnerability has been resolved:

binder: fix memory leak in binder_init()

In binder_init(), the destruction of binder_alloc_shrinker_init() is not

performed in the wrong path, which will cause memory leaks. So this commit

introduces binder_alloc_shrinker_exit() and calls it in the wrong path to

fix that.