platform/x86: fujitsu-laptop: Fix radio LED detection

Radio LED detection method implemented in commit 4f62568c1fcf
("fujitsu-laptop: Support radio LED") turned out to be incorrect as it
causes a radio LED to be erroneously detected on a Fujitsu Lifebook E751
which has a slide switch (and thus no radio LED).  Use bit 17 of
flags_supported (the value returned by method S000 of ACPI device
FUJ02E3) to determine whether a radio LED is present as it seems to be a
more reliable indicator, based on comparing DSDT tables of four Fujitsu
Lifebook models (E744, E751, S7110, S8420).

Fixes: 4f62568c1fcf ("fujitsu-laptop: Support radio LED")
Reported-by: Heinrich Siebmanns <harv@gmx.de>
Signed-off-by: Michał Kępień <kernel@kempniu.pl>
Tested-by: Heinrich Siebmanns <harv@gmx.de>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

drivers/platform/x86/fujitsu-laptop.c

@@ -691,6 +691,7 @@ static enum led_brightness eco_led_get(struct led_classdev *cdev)
 
 static int acpi_fujitsu_laptop_leds_register(struct acpi_device *device)
 {
+	struct fujitsu_laptop *priv = acpi_driver_data(device);
 	struct led_classdev *led;
 	int result;
 
@@ -724,12 +725,15 @@ static int acpi_fujitsu_laptop_leds_register(struct acpi_device *device)
 	}
 
 	/*
-	 * BTNI bit 24 seems to indicate the presence of a radio toggle
-	 * button in place of a slide switch, and all such machines appear
-	 * to also have an RF LED.  Therefore use bit 24 as an indicator
-	 * that an RF LED is present.
+	 * Some Fujitsu laptops have a radio toggle button in place of a slide
+	 * switch and all such machines appear to also have an RF LED.  Based on
+	 * comparing DSDT tables of four Fujitsu Lifebook models (E744, E751,
+	 * S7110, S8420; the first one has a radio toggle button, the other
+	 * three have slide switches), bit 17 of flags_supported (the value
+	 * returned by method S000 of ACPI device FUJ02E3) seems to indicate
+	 * whether given model has a radio toggle button.
 	 */
-	if (call_fext_func(device, FUNC_BUTTONS, 0x0, 0x0, 0x0) & BIT(24)) {
+	if (priv->flags_supported & BIT(17)) {
 		led = devm_kzalloc(&device->dev, sizeof(*led), GFP_KERNEL);
 		if (!led)
 			return -ENOMEM;