exynos/drm: hdmi: cleanup for hdmi common device registration

The hdmi common device registration function does not need extern definition
and for error case and unregister case, exynos_drm_hdmi_pdev should be cleared.
Signed-off-by: Seung-Woo Kim <sw0312.kim@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>

drivers/gpu/drm/exynos/exynos_drm_drv.h

@@ -322,7 +322,7 @@ void exynos_drm_subdrv_close(struct drm_device *dev, struct drm_file *file);
  * this function registers exynos drm hdmi platform device. It ensures only one
  * instance of the device is created.
  */
-extern int exynos_platform_device_hdmi_register(void);
+int exynos_platform_device_hdmi_register(void);
 
 /*
  * this function unregisters exynos drm hdmi platform device if it exists.

drivers/gpu/drm/exynos/exynos_drm_hdmi.c

@@ -51,21 +51,27 @@ struct drm_hdmi_context {
 
 int exynos_platform_device_hdmi_register(void)
 {
+	struct platform_device *pdev;
+
 	if (exynos_drm_hdmi_pdev)
 		return -EEXIST;
 
-	exynos_drm_hdmi_pdev = platform_device_register_simple(
+	pdev = platform_device_register_simple(
 			"exynos-drm-hdmi", -1, NULL, 0);
-	if (IS_ERR(exynos_drm_hdmi_pdev))
-		return PTR_ERR(exynos_drm_hdmi_pdev);
+	if (IS_ERR(pdev))
+		return PTR_ERR(pdev);
+
+	exynos_drm_hdmi_pdev = pdev;
 
 	return 0;
 }
 
 void exynos_platform_device_hdmi_unregister(void)
 {
-	if (exynos_drm_hdmi_pdev)
+	if (exynos_drm_hdmi_pdev) {
 		platform_device_unregister(exynos_drm_hdmi_pdev);
+		exynos_drm_hdmi_pdev = NULL;
+	}
 }
 
 void exynos_hdmi_drv_attach(struct exynos_drm_hdmi_context *ctx)