radv: flush and invalidate CB before resetting query pools on GFX9

radv: flush and invalidate CB before resetting query pools on GFX9

We have to emit a CACHE_FLUSH_AND_INV_TS_EVENT to be sure all
prior GPU work is done. While we are at it, also flush and
invalidate DB.

This fixes the following CTS (when the small hint is disabled):
dEQP-VK.query_pool.statistics_query.reset_before_copy.*

Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-By: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>