drm/msm/dsi: Fix potential NULL pointer dereference in msm_dsi_modeset_init

_dev_ is being dereferenced before it is null checked, hence there
is a potential null pointer dereference.

Fix this by moving the pointer dereference after _dev_ has been
null checked.

Fixes: d4e7f38d70ef ("drm/msm/dsi: check msm_dsi and dsi pointers before use")
Signed-off-by: Gustavo A. R. Silva <garsilva@embeddedor.com>
Signed-off-by: Rob Clark <robdclark@gmail.com>

drivers/gpu/drm/msm/dsi/dsi.c

@@ -192,13 +192,14 @@ void __exit msm_dsi_unregister(void)
 int msm_dsi_modeset_init(struct msm_dsi *msm_dsi, struct drm_device *dev,
 			 struct drm_encoder *encoder)
 {
-	struct msm_drm_private *priv = dev->dev_private;
+	struct msm_drm_private *priv;
 	struct drm_bridge *ext_bridge;
 	int ret;
 
 	if (WARN_ON(!encoder) || WARN_ON(!msm_dsi) || WARN_ON(!dev))
 		return -EINVAL;
 
+	priv = dev->dev_private;
 	msm_dsi->dev = dev;
 
 	ret = msm_dsi_host_modeset_init(msm_dsi->host, dev);