liverpool: Write valid queries on PixelPipeStatDump (#3553)

* liverpool: Write valid queries on PixelPipeStatDump

* export: Small assert swap

* liverpool: Advance zpass counter on every dump request

src/video_core/amdgpu/liverpool.h

@@ -1666,6 +1666,8 @@ private:
     u32 num_mapped_queues{1u}; // GFX is always available
 
     VAddr indirect_args_addr{};
+    u32 num_counter_pairs{};
+    u64 pixel_counter{};
 
     struct ConstantEngine {
         void Reset() {