intel: Emit 3DSTATE_VF_STATISTICS dynamically

Pipeline statistics queries should not count BLORP's rectangles.

    (23) How do operations like Clear, TexSubImage, etc. affect the
         results of the newly introduced queries?

      DISCUSSION: Implementations might require "helper" rendering
      commands be issued to implement certain operations like Clear,
      TexSubImage, etc.

      RESOLVED: They don't. Only application submitted rendering
      commands should have an effect on the results of the queries.

Piglit's arb_pipeline_statistics_query-vert_adj exposes this bug when
the driver is hacked to always perform glBufferData via a GPU staging
copy (for debugging purposes).

Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>

src/intel/vulkan/genX_blorp_exec.c

@@ -258,11 +258,6 @@ genX(blorp_exec)(struct blorp_batch *batch,
     */
    genX(cmd_buffer_enable_pma_fix)(cmd_buffer, false);
 
-   /* Disable VF statistics */
-   blorp_emit(batch, GENX(3DSTATE_VF_STATISTICS), vf) {
-      vf.StatisticsEnable = false;
-   }
-
    blorp_exec(batch, params);
 
    cmd_buffer->state.gfx.vb_dirty = ~0;