virgl: track valid buffer range and fix a transfer issue
This replaces virgl_transfer_queue_is_queued by the tracking of valid buffer range for skipping flushes. This is a correctness fix that might regress the performances in some cases.
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This replaces virgl_transfer_queue_is_queued by the tracking of valid buffer range for skipping flushes. This is a correctness fix that might regress the performances in some cases.