drm/exynos: check for null pointers in error handling

Smatch error from arm build: drivers/gpu/drm/exynos/
exynos_hdmi.c:2374 hdmi_probe() error: potential NULL
dereference 'hdata->hdmiphy_port'.

Added check for hdata->hdmiphy_port that it is not NULL.
Signed-off-by: NPaul Taysom <taysom@chromium.org>
Signed-off-by: NRahul Sharma <Rahul.Sharma@samsung.com>
Signed-off-by: NInki Dae <inki.dae@samsung.com>

drivers/gpu/drm/exynos/exynos_hdmi.c

@@ -2174,6 +2174,7 @@ static int hdmi_probe(struct platform_device *pdev)
 	return exynos_drm_component_add(&pdev->dev, &hdmi_component_ops);
 
 err_hdmiphy:
+	if (hdata->hdmiphy_port)
 		put_device(&hdata->hdmiphy_port->dev);
 err_ddc:
 	put_device(&hdata->ddc_adpt->dev);