lib/kmstest: Fix up tiled buffer creation

When extracting a raw __gem_set_tiling helper I've fumbled this in

commit 590f610140
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date:   Wed Oct 9 20:50:50 2013 +0200

    lib/drmtest: extract rawer __gem_set_tiling

Fix things up so that we properly propaget the error again.

Now to make this all properly work we also need to make kms_flip a
notch more robust against such failures ...

This only blows up on gen2/3 with the pan tests which want a too wide
framebuffer for tiling.

Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

lib/igt_kms.c

@@ -56,7 +56,6 @@
  * Note that this library's header pulls in the [i-g-t framebuffer](intel-gpu-tools-i-g-t-framebuffer.html)
  * library as a dependency.
  */
-
 const char *kmstest_pipe_str(int pipe)
 {
 	const char *str[] = { "A", "B", "C" };