radv: only emit ZPASS_DONE for timestamp queries on gfx queues

A ZPASS_DONE packet doesn't make sense for the compute queue. It will
result in a gpu hang.

This change resolves a gpu hang for SteamVR+Vega.

Cc: mesa-stable@lists.freedesktop.org
Fixes: 1f616a84 "radv: emit a dummy ..."
Signed-off-by: Andres Rodriguez <andresx7@gmail.com>
Reviewed-by: Dave Airlie <airlied@redhat.com>
(cherry picked from commit ec1fcf92)