iris: Replace unconditional QBO flush with iris_dirty_for_history().

We can now use the same cache tracking mechanism for synchronizing QBO
writes instead of the unconditional PIPE_CONTROL performed currently,
which is unable to invalidate any incoherent caches which may contain
stale data for the buffer object.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/15738>
1 file changed