radv: use a compute shader for copying timestamp query results

radv: use a compute shader for copying timestamp query results

When the timestamp is not ready (ie. UINT64_MAX), the availabily bit
should be zero. The previous code used to copy the timestamp value
as the availabily bit and that's completely wrong.

Because it's not that simple to emit a conditional with the CP, the
driver now uses a compute shader for copying timestamp query results.

Fixes dEQP-VK.pipeline.timestamp.misc_tests.reset_query_before_copy.

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