platform/x86: asus-wmi: Fix keyboard brightness cannot be set to 0

BugLink: https://bugs.launchpad.net/bugs/1860681

commit 176a7fca upstream.

Some of ASUS laptops like UX431FL keyboard backlight cannot be set to
brightness 0. According to ASUS' information, the brightness should be
0x80 ~ 0x83. This patch fixes it by following the logic.

Fixes: e9809c0b ("asus-wmi: add keyboard backlight support")
Signed-off-by: Jian-Hong Pan <jian-hong@endlessm.com>
Reviewed-by: Daniel Drake <drake@endlessm.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Connor Kuehl <connor.kuehl@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

drivers/platform/x86/asus-wmi.c

@@ -452,13 +452,7 @@ static void kbd_led_update(struct work_struct *work)
 
 	asus = container_of(work, struct asus_wmi, kbd_led_work);
 
-	/*
-	 * bits 0-2: level
-	 * bit 7: light on/off
-	 */
-	if (asus->kbd_led_wk > 0)
-		ctrl_param = 0x80 | (asus->kbd_led_wk & 0x7F);
-
+	ctrl_param = 0x80 | (asus->kbd_led_wk & 0x7F);
 	asus_wmi_set_devstate(ASUS_WMI_DEVID_KBD_BACKLIGHT, ctrl_param, NULL);
 }