acer-wmi: Port to new backlight interface selection API

Port the backlight selection logic to the new backlight interface
selection API.

This commit also removes various obsolete pr_xxx messages related to
backlight interface selection. These are obsolete because they assume
there is only a vendor or acpi backlight driver and no other choice.
Also they are not necessary, if the user wants to know which backlight
interfaces are registered a simple "ls /sys/class/backlight" suffices.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Lee, Chun-Yi <jlee@suse.com>
Acked-by: Darren Hart <dvhart@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/platform/x86/acer-wmi.c

@@ -2246,14 +2246,10 @@ 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()) {
+		acpi_video_set_dmi_backlight_type(acpi_backlight_vendor);
+
+	if (acpi_video_get_backlight_type() != acpi_backlight_vendor)
 		interface->capability &= ~ACER_CAP_BRIGHTNESS;
-		pr_info("Brightness must be controlled by acpi video driver\n");
-	} else {
-		pr_info("Disabling ACPI video driver\n");
-		acpi_video_unregister_backlight();
-	}
 
 	if (wmi_has_guid(WMID_GUID3)) {
 		if (ec_raw_mode) {