benchmarks: Add simple pread/pwrite benchmarks

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
diff --git a/benchmarks/.gitignore b/benchmarks/.gitignore
index 09e5bd8..20b390e 100644
--- a/benchmarks/.gitignore
+++ b/benchmarks/.gitignore
@@ -1,3 +1,5 @@
+gem_exec_nop
+gem_prw
 gem_userptr_benchmark
 intel_upload_blit_large
 intel_upload_blit_large_gtt