drm/tegra: dc: Return planar flag for non-YUV modes

This prevents the compiler from warning about using a variable that is
possibly uninitialized.

Signed-off-by: Thierry Reding <treding@nvidia.com>
diff --git a/drivers/gpu/drm/tegra/dc.c b/drivers/gpu/drm/tegra/dc.c
index a56fccc..c2ab1a2 100644
--- a/drivers/gpu/drm/tegra/dc.c
+++ b/drivers/gpu/drm/tegra/dc.c
@@ -134,6 +134,9 @@
 		return true;
 	}
 
+	if (planar)
+		*planar = false;
+
 	return false;
 }