benchmarks: Add kms_vblank to .gitignore

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
diff --git a/benchmarks/.gitignore b/benchmarks/.gitignore
index 2c9d044..68f8f1d 100644
--- a/benchmarks/.gitignore
+++ b/benchmarks/.gitignore
@@ -6,4 +6,5 @@
 intel_upload_blit_large_gtt
 intel_upload_blit_large_map
 intel_upload_blit_small
+kms_vblank
 # Please keep sorted alphabetically