anv: Add support for the PMA fix on Broadwell

This helps Dota 2 on Broadwell by 8-9%.  I also hacked up the driver and
used the Sascha "shadowmapping" demo to get some results.  Setting
uses_kill to true dropped the framerate on the demo by 25-30%.  Enabling
the PMA fix brought it back up to around 90% of the original framerate.

Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: Nanley Chery <nanley.g.chery@intel.com>

src/intel/vulkan/genX_blorp_exec.c

@@ -154,6 +154,11 @@ genX(blorp_exec)(struct blorp_batch *batch,
 
    genX(cmd_buffer_emit_gen7_depth_flush)(cmd_buffer);
 
+   /* BLORP doesn't do anything fancy with depth such as discards, so we want
+    * the PMA fix off.  Also, off is always the safe option.
+    */
+   genX(cmd_buffer_enable_pma_fix)(cmd_buffer, false);
+
    blorp_exec(batch, params);
 
    cmd_buffer->state.vb_dirty = ~0;