* Implement GPU syncpoints This adds support for GPU syncpoints on the GPU backend & nvservices. Everything that was implemented here is based on my researches, hardware testing of the GM20B and reversing of nvservices (8.1.0). Thanks to @fincs for the informations about some behaviours of the pusher and for the initial informations about syncpoints. * syncpoint: address gdkchan's comments * Add some missing logic to handle SubmitGpfifo correctly * Handle the NV event API correctly * evnt => hostEvent * Finish addressing gdkchan's comments * nvservices: write the output buffer even when an error is returned * dma pusher: Implemnet prefetch barrier lso fix when the commands should be prefetch. * Partially fix prefetch barrier * Add a missing syncpoint check in QueryEvent of NvHostSyncPt * Address Ac_K's comments and fix GetSyncpoint for ChannelResourcePolicy == Channel * fix SyncptWait & SyncptWaitEx cmds logic * Address ripinperi's comments * Address gdkchan's comments * Move user event management to the control channel * Fix mm implementation, nvdec works again * Address ripinperi's comments * Address gdkchan's comments * Implement nvhost-ctrl close accurately + make nvservices dispose channels when stopping the emulator * Fix typo in MultiMediaOperationType