drm/tegra: Add Tegra186 display hub support

Hello Thierry Reding,

This is a semi-automatic email about new static checker warnings.

The patch c4755fb9064f: "drm/tegra: Add Tegra186 display hub support" from Nov 13, 2017, leads to the following Smatch complaint:

drivers/gpu/drm/tegra/hub.c:375 tegra_shared_plane_atomic_disable()
warn: variable dereferenced before check 'old_state' (see line 370)

drivers/gpu/drm/tegra/hub.c
369 {

   370		struct tegra_dc *dc = to_tegra_dc(old_state->crtc);
                                                  ^^^^^^^^^^^^^^^

Deref

371 struct tegra_plane *p = to_tegra_plane(plane);
372 u32 value;
373
374 /* rien ne va plus */
375 if (!old_state || !old_state->crtc)

                     ^^^^^^^^^

Check too late.

376 return;
377

regards,
dan carpenter