drm/msi/mdp4: populate priv->kms in mdp4_kms_init

Without this fix boot throws NULL ptr exception at msm_dsi_manager_setup_encoder
on devices like Nexus 7 2013 (MDP4 v4.4).

Fixes: 03436e3e ("drm/msm/dsi: Move setup_encoder to modeset_init")

Cc: <stable@vger.kernel.org>
Signed-off-by: David Heidelberg <david@ixit.cz>
Link: https://lore.kernel.org/r/20210811170631.39296-1-david@ixit.czSigned-off-by: Rob Clark <robdclark@chromium.org>

drivers/gpu/drm/msm/disp/mdp4/mdp4_kms.c

@@ -399,6 +399,7 @@ struct msm_kms *mdp4_kms_init(struct drm_device *dev)
 {
 	struct platform_device *pdev = to_platform_device(dev->dev);
 	struct mdp4_platform_config *config = mdp4_get_config(pdev);
+	struct msm_drm_private *priv = dev->dev_private;
 	struct mdp4_kms *mdp4_kms;
 	struct msm_kms *kms = NULL;
 	struct msm_gem_address_space *aspace;
@@ -418,7 +419,8 @@ struct msm_kms *mdp4_kms_init(struct drm_device *dev)
 		goto fail;
 	}
 
-	kms = &mdp4_kms->base.base;
+	priv->kms = &mdp4_kms->base.base;
+	kms = priv->kms;
 
 	mdp4_kms->dev = dev;