* 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
