drm/sun4i: add missing put_device() call in sun8i_r40_tcon_tv_set_mux()

If sun8i_r40_tcon_tv_set_mux() succeed, sun8i_r40_tcon_tv_set_mux()
doesn't have a corresponding put_device(). Thus add put_device()
to fix the exception handling for this function implementation.

Fixes: 0305189a ("drm/sun4i: tcon: Add support for R40 TCON")
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://patchwork.freedesktop.org/patch/msgid/20200826010826.1785487-1-yukuai3@huawei.com

drivers/gpu/drm/sun4i/sun4i_tcon.c

@@ -1433,14 +1433,18 @@ static int sun8i_r40_tcon_tv_set_mux(struct sun4i_tcon *tcon,
 	if (IS_ENABLED(CONFIG_DRM_SUN8I_TCON_TOP) &&
 	    encoder->encoder_type == DRM_MODE_ENCODER_TMDS) {
 		ret = sun8i_tcon_top_set_hdmi_src(&pdev->dev, id);
-		if (ret)
+		if (ret) {
+			put_device(&pdev->dev);
 			return ret;
+		}
 	}
 
 	if (IS_ENABLED(CONFIG_DRM_SUN8I_TCON_TOP)) {
 		ret = sun8i_tcon_top_de_config(&pdev->dev, tcon->id, id);
-		if (ret)
+		if (ret) {
+			put_device(&pdev->dev);
 			return ret;
+		}
 	}
 
 	return 0;