Add/correct a2xx performance counters.

During reverse-engineering I found out there are additional RB and RBBM performance counters which are not (or wrongly) reflected in the register file.

As this was discovered on a Xenos GPU I submit this as a "Draft" since I am unable to test/confirm this on a real Adreno 2xx (although I have a Adreno 200 phone but never installed Linux/mesa on it).