ACPI / video: Revert "thinkpad_acpi: Use acpi_video_handles_brightness_key_presses()"

acpi_video_handles_brightness_key_presses()'s may return false if the i915
driver is not loaded yet when thinkpad_acpi loads, and then return true
after the i915 driver has loaded. This means that thinkpad_acpi cannot
use it as is since thinkpad_acpi caches the return value.

This reverts commit 7714687a ("thinkpad_acpi: Use
acpi_video_handles_brightness_key_presses()").

Fixes: 7714687a "thinkpad_acpi: Use acpi_video_handles_brightness_key_presses()"
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Darren Hart <dvhart@linux.intel.com>
Acked-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/platform/x86/thinkpad_acpi.c

@@ -3488,7 +3488,7 @@ static int __init hotkey_init(struct ibm_init_struct *iibm)
 	/* Do not issue duplicate brightness change events to
 	 * userspace. tpacpi_detect_brightness_capabilities() must have
 	 * been called before this point  */
-	if (acpi_video_handles_brightness_key_presses()) {
+	if (acpi_video_get_backlight_type() != acpi_backlight_vendor) {
 		pr_info("This ThinkPad has standard ACPI backlight "
 			"brightness control, supported by the ACPI "
 			"video driver\n");