drm/dp: add a hw mutex around the transfer functions. (v2)

This should avoid races between connector probing and HPD
irqs in the future, currently mode_config.mutex blocks this
possibility.

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/tegra/dpaux.c

@@ -332,7 +332,7 @@ static int tegra_dpaux_probe(struct platform_device *pdev)
 	dpaux->aux.transfer = tegra_dpaux_transfer;
 	dpaux->aux.dev = &pdev->dev;
 
-	err = drm_dp_aux_register_i2c_bus(&dpaux->aux);
+	err = drm_dp_aux_register(&dpaux->aux);
 	if (err < 0)
 		return err;
 
@@ -355,7 +355,7 @@ static int tegra_dpaux_remove(struct platform_device *pdev)
 {
 	struct tegra_dpaux *dpaux = platform_get_drvdata(pdev);
 
-	drm_dp_aux_unregister_i2c_bus(&dpaux->aux);
+	drm_dp_aux_unregister(&dpaux->aux);
 
 	mutex_lock(&dpaux_lock);
 	list_del(&dpaux->list);