Use -Werror in frameworks/native/services/vr

* Fix/remove unused variables, parameters, functions.
* Add missing typedef name.
* Suppress warning of unused return value from release().
* Suppress warnings that are fixed in goog/master, to be exported to AOSP.

Bug: 66996870
Test: build with WITH_TIDY=1
Change-Id: If6b539db0a243b44fc6d51d90259f6564f306f6d