libbinder_ndk: _delete APIs take * not **.

Since having ** requires having a pointer allocated on the stack. This
is pretty common if you are using an object within a scope, but causes
problems when it is not.

Bug: 111445392
Test: ./ndk/runtests.sh
Change-Id: If7586548af0b47d8e09178fc3b71af50d449e290