drm/i915: Fix updating FBC

We need to track different state on each generation in order to detect
when we need to refresh the FBC registers.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index 3d882b7..fb5c2a6 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -719,6 +719,9 @@
 	} else {
 		seq_printf(m, "FBC disabled: ");
 		switch (dev_priv->no_fbc_reason) {
+		case FBC_NO_OUTPUT:
+			seq_printf(m, "no outputs");
+			break;
 		case FBC_STOLEN_TOO_SMALL:
 			seq_printf(m, "not enough stolen memory");
 			break;