libbinder_ndk: clarify local AIBinder_linkToDeath

When a binder is local, process death means that the client calling
linkToDeath will also die. In this case, there is no need to use a
death recipient, so an error is returned.

Bug: 112664205
Test: atest android.binder.cts
Change-Id: I675637e937c1ac7a584a2d97bb1238e5b9f3e030