Most applications call AcquireRight before calling RegisterInterruptRelayQueue so we can't assign the thread id there.
This fixes the bug with LLE applets not launching properly.
This is true for all interrupts except PDC0 and PDC1, which should be triggered for all registered threads.
TODO: The real GSP module seems to only trigger PDC0 after updating the screens (both top and bottom). PDC1 doesn't seem to be triggered at all.
The registered interrupt event is unique to each session that calls RegisterInterruptRelayQueue, and only that event should be reset when UnregisterInterruptRelayQueue is called.
The only functional change is the error handling of GSP_GPU::ReadHWRegs function. We previously didn't return error codes (not even for success). The new returns were found by reverse engineering the GSP module.
