drm/i915: VCS is not the last ring

I made a mistake, please forgive me.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=48254
Signed-off-by: Ben Widawsky <benjamin.widawsky@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_debugfs.c

@@ -742,7 +742,7 @@ static void i915_ring_error_state(struct seq_file *m,
 				  struct drm_i915_error_state *error,
 				  unsigned ring)
 {
-	BUG_ON(ring > VCS); /* shut up confused gcc */
+	BUG_ON(ring >= I915_NUM_RINGS); /* shut up confused gcc */
 	seq_printf(m, "%s command stream:\n", ring_str(ring));
 	seq_printf(m, "  HEAD: 0x%08x\n", error->head[ring]);
 	seq_printf(m, "  TAIL: 0x%08x\n", error->tail[ring]);