thinkpad-acpi: fix issuing duplicated key events for brightness up/down

commit ff413195 upstream.

The tp_features.bright_acpimode will not be set correctly for brightness
control because ACPI_VIDEO_HID will not be located in ACPI. As a result,
a duplicated key event will always be sent. acpi_video_backlight_support()
is sufficient to detect standard ACPI brightness control.
Signed-off-by: Alex Hung <alex.hung@canonical.com>
Signed-off-by: Matthew Garrett <mjg@redhat.com>
Cc: Andreas Sturmlechner <andreas.sturmlechner@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/platform/x86/thinkpad_acpi.c

@@ -3402,7 +3402,7 @@ 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 (tp_features.bright_acpimode && acpi_video_backlight_support()) {
+	if (acpi_video_backlight_support()) {
 		pr_info("This ThinkPad has standard ACPI backlight "
 			"brightness control, supported by the ACPI "
 			"video driver\n");