radv: fix events on compute queues.

The event emission wasn't sending the correct packet for gfx8 compute
queues, which explains why it works on vega fine.

This fixes the mpv vulkan hang.

Fixes: ad61eac2 (radv: factor out eop event writing code. (v2))
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Signed-off-by: Dave Airlie <airlied@redhat.com>
(cherry picked from commit 38e4467e)