drivers-platform-x86: use acpi_video_dmi_promote_vendor()

Instead of using directly acpi_video_unregister(), use
acpi_video_dmi_promote_vendor() (and make it call
acpi_video_unregister() if needed)

Signed-off-by: Corentin Chary <corentin.chary@gmail.com>
Signed-off-by: Matthew Garrett <mjg@redhat.com>

drivers/platform/x86/acer-wmi.c

@@ -2191,14 +2191,16 @@ static int __init acer_wmi_init(void)
 
 	set_quirks();
 
+	if (dmi_check_system(video_vendor_dmi_table))
+		acpi_video_dmi_promote_vendor();
 	if (acpi_video_backlight_support()) {
-		if (dmi_check_system(video_vendor_dmi_table)) {
-			acpi_video_unregister();
-		} else {
-			interface->capability &= ~ACER_CAP_BRIGHTNESS;
-			pr_info("Brightness must be controlled by "
-				"acpi video driver\n");
-		}
+		interface->capability &= ~ACER_CAP_BRIGHTNESS;
+		pr_info("Brightness must be controlled by acpi video driver\n");
+	} else {
+#ifdef CONFIG_ACPI_VIDEO
+		pr_info("Disabling ACPI video driver\n");
+		acpi_video_unregister();
+#endif
 	}
 
 	if (wmi_has_guid(WMID_GUID3)) {