Skip the zero-index perfcntr collection only if CP_ALWAYS_COUNT is used,
since we want to collect that at the very end/start of collection. But
don't unwittingly ignore that perfcntr if CP_ALWAYS_COUNT isn't being
collected.
Signed-off-by: Zan Dobersek <zdobersek@igalia.com>
Fixes: 86456cf0e6 ("tu: support exposing derived counters through VK_KHR_performance_query")
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/33852>